Skip to content

HTTPS clone URL

Subversion checkout URL

You can clone with
or
.
Download ZIP
Browse files

Merge remote branch 'jnavila/master'

Conflicts:
	fr/01-introduction/01-chapter1.markdown
  • Loading branch information...
commit 25c0e8837a9cf3be135dcd32600788a359437033 2 parents 459a07e + 9bc06ca
@schacon schacon authored
View
1  .gitattributes
@@ -0,0 +1 @@
+*.graffle binary
View
232 fr/01-introduction/01-chapter1.markdown
@@ -1,225 +1,225 @@
-# Pour commencer #
+# Démarrage rapide #
-Ce chapitre concernera la prise en main de Git. Nous commencerons par introduire les outils de suivi de version, puis continuerons avec l'installation de Git sur votre système pour terminer par sa configuration opérationnelle. A la fin de ce chapitre vous devriez comprendre pourquoi Git a été créé, pourquoi vous devrier l'utiliser et comment ce faire.
+Ce chapitre traite du démarrage rapide avec Git. Nous commencerons par expliquer les bases des gestions de version, puis nous parlerons de l'installation de Git sur votre système et finalement comment le paramétrer pour commencer à l'utiliser. A la fin de ce chapitre vous devriez en savoir assez pour comprendre pourquoi on parle beaucoup de Git, pourquoi vous devriez l'utiliser et vous devriez en avoir une installation prête à l'emploi.
-## A propos du suivi de version ##
+## À propos de la gestion de version ##
-Qu'est-ce que le suivi de version, et pourquoi devriez-vous vous en soucier ? Le suivi de version est un système qui enregistre les modifications apportées dans le temps à un fichier ou un lot de fichiers de manière à pouvoir en récupérer une copie spécifique ultérieurement. Dans le cadre des exemples fournis dans cet ouvrage, vous utiliserez du code source comme matière première à soumettre au suivi de version, mais en réalité vous pouvez le faire avec quasiment n'importe quel type de fichier présent sur votre ordinateur.
+Qu'est-ce que la gestion de version et pourquoi devriez-vous vous en soucier ? La gestion de version est un système qui enregistre l'évolution d'un fichier ou d'un ensemble de fichiers au cours du temps de manière à ce qu'on puisse rappeler une version antérieure d'un fichier à tout moment. Pour les exemples de ce livre, nous utiliserons des fichiers sources de logiciel comme fichiers sous gestion de version, bien qu'en réalité on puisse l'utiliser avec pratiquement tous les types de fichiers d'un ordinateur.
-Si vous êtes graphiste ou concepteur de sites Web et désirez conserver chacune des versions d'une image ou d'un gabarit (ce que vous voulez certainement), un système de suivi de version (SSV) offre une sage solution. Il permet de restaurer un fichier à sa version précédente, rétablir à une version antérieure l'ensemble d'un projet, comparer les modifications au fil du temps, repérer qui a effectué récemment un changement susceptible d'être à la source d'un problème, quand est apparue une problématique et qui l'a introduite, etc. Utiliser un SSV signifie également la possibilité de se remettre facilement d'une catastrophe ou d'une perte de fichier. Tout cela, presque sans effort supplémentaire.
+Si vous êtes un dessinateur ou un designer web et voulez conserver toutes les versions d'une image ou d'une mise en page (ce que vous voudriez surement faire), un système de gestion de version (VCS en anglais pour Version Control System) est un outil qu'il est très sage d'utiliser. Il vous permet de ramener un fichier à un état précédent, ramener le projet complet à un état précédent, comparer les changements au cours du temps, voir qui a modifié quelque chose qui pourrait causer un problème, qui a introduit un problème et quand, et plus encore. Utiliser un VCS signifie aussi généralement que si vous vous trompez ou vous perdez des fichiers, vous pouvez facilement revenir à un état stable. De plus, vous obtenez tous ces avantages pour peu de surcharge de travail.
-### Systèmes locaux de suivi de version ###
+### Les systèmes de gestion de version locaux ###
-Pour de nombreuses personnes, la méthode de choix pour la sauvegarde consiste à copier des fichiers dans un autre répertoire (peut-être nommé après la date courante, dans le meilleur des cas). Cette approche est très populaire du fait de sa simplicité, mais aussi incroyablement susceptible d'erreur. Il est tellement simple d'oublier le répertoire courant et modifier accidentellement le mauvais fichier ou en écraser un autre sans le vouloir.
+La méthode commune pour la gestion de version est généralement de recopier les fichiers dans un autre répertoire (peut-être avec un nom incluant la date pour les plus malins). Cette méthode est la plus commune parce que c'est la plus simple, mais c'est aussi la plus grande source d'erreurs. Il est facile d'oublier le répertoire dans lequel vous êtes et d'écrire accidentellement dans le mauvais fichier ou d'écraser des fichiers que vous vouliez conserver.
-Afin d'éviter cet écueil, les programmeurs ont depuis longtemps développé des SSV dotés d'une base de données simple conservant les modifications apportées aux fichiers suivis (voir la figure 1-1).
+Pour traiter ce problème, les programmeurs ont développé il y a longtemps des VCSs locaux qui utilisaient une base de données simple pour conserver les modifications d'un fichier (Cf. figure 1-1).
-Insert 18333fig0101.png
-Figure 1-1. Diagramme du suivi local de version
+Insert 18333fig0101.png
+Figure 1-1. Diagramme des systèmes de gestion de version locaux.
-RCS, l'un des SSV les plus populaires, est encore fourni avec la plupart des ordinateurs. Même le célèbre Mac OS X inclue la commande rcs lorsque vous installez la suite de développement. Schématiquement, cet outil fonctionne en conservant dans un format spécial sur le disque des lots de corrections (c'est-à-dire les différences entre les fichiers) d'une sauvegarde à l'autre; il peut restituer l'état d'un fichier à un instant quelconque en appliquant l'ensemble des corrections jusqu'à cet instant.
+Un des systèmes les plus populaires était rcs, qui est encore distribué avec de nombreux systèmes d'exploitation aujourd'hui. Même le système d'exploitation populaire Mac OS X inclut le programme rcs lorsqu'on installe les outils de développement logiciel. Cet outil fonctionne en conservant les patch sets (c'est-à-dire la différence entre les fichiers) d'une version à l'autre dans un format spécial sur disque ; il peut alors recréer ce qu'était n'importe quel fichier à n'importe quel instant en ajoutant toutes les différences.
-### Systèmes centralisés de suivi de version ###
+### Les systèmes de gestion de version centralisés ###
-La problématique majeure que rencontre ensuite la plupart des gens est la nécessité de collaborer avec des développeurs sur d'autres systèmes. Les systèmes centralisés de suivi de version (SCSV) ont été créé pour répondre à ce besoin. Ces systèmes, tels CVS, Subversion et Perforce, disposent d'un serveur unique maintenant l'ensemble des des versions des fichiers suivis, et des clients qui récupèrent leurs copies depuis ce serveur centrale. Depuis des années ce modèle s'établit comme le standard du suivi de versions (voir la figure 1-2).
+Le problème majeur suivant que les gens rencontrent est qu'ils ont besoin de collaborer avec des développeurs sur d'autres ordinateurs. Pour traiter ce problème, les systèmes de gestion de version centralisés (CVCS en anglais pour Centralized Version Control Systems) furent développés. Ces systèmes tels que CVS, Subversion, et Perforce, mettent en place un serveur central qui contient tous les fichiers sous version, et des clients qui peuvent extraire les fichiers de ce dépot central. Pendant de nombreuses années, celà a été le standard pour la gestion de version (Cf. Figure 1-2).
-Insert 18333fig0102.png
-Figure 1-2. Diagramme des systèmes centralisés de suivi de version.
+Insert 18333fig0102.png
+Figure 1-2. Diagramme de la gestion de version centralisée.
-Ce modèle offre de nombreux avantages, surtout comparé aux SSV locaux. Par exemple, chacun sait jusqu'à un certain point, ce à quoi tout les autres sur le projet est occupé. Les administrateurs disposent d'une maîtrise fine des prérogatives de chacun; et il est bien plus facile de gérer un SCSV que d'avoir à maintenir des bases de données locales sur chaque machine cliente.
+Ce schéma offre de nombreux avantages par rapport à la gestion de version locale. Par exemple, chacun sait jusqu'à un certain point ce que tout les autres sont en train de faire sur le projet. Les administrateurs ont un contrôle fin des permissions et il est beaucoup plus facile d'administrer un CVCS qu'il l'est de devoir gérer des bases de données locales.
-Cependant, ce modèle souffre de sérieux écueils. Le plus évident concerne le point unique de panne que représente le serveur central. Si ce serveur devient indisponible pendant une heure, durant tout ce temps personne ne pourra collaborer ni sauvegarder les modifications de ses propres travaux en cours. Si le disque dur de la base de données centrale est corrompu, et que des sauvegardes suffisantes n'ont pas été prévues, c'est l'ensemble du projet que vous pouvez perdre-incluant son historique, à l'exception de quelque copie intégrale dont pourraient disposer certaines personnes sur leurs propres machines. Les SSV locaux souffrent du même problème-dès que vous entreposez l'intégralité de l'historique d'un projet dans un endroit unique, vous risquez de tout perdre.
+Cependant ce système a aussi de nombreux défauts. Le plus visible est le point unique de panne que le serveur centralisé représente. Si ce serveur est en panne pendant une heure, alors durant cette heure, aucun client ne peut collaborer ou enregistrer les modifications issues de son travail. Si le disque dur du serveur central se corrompt, et s'il n'y a pas eu de sauvegarde, vous perdez absolument tout de l'historique d'un projet en dehors des sauvegardes locales que les gens auraient pu réaliser sur leur machines locales. Les systèmes de gestion de version locaux souffrent du même problème - dès qu'on a tout l'historique d'un projet sauvegardé à un endroit unique, on prend le risque de tout perdre.
-### Les systèmes distribués de suivi de version ###
+### Les systèmes de gestion de version distribués ###
-C'est là que les systèmes distribués de suivi de version apparaissent. Dans un SDSV (comme Git, Mercurial, Bazaar ou Darcs), les clients ne récupèrent pas seulement la dernière copie des fichiers : ils maintiennent localement un miroir fidèle du dépôt. Si l'un quelconque des serveurs disparait, et que ces systèmes collaboraient avec lui, chacun des clients saura fournir une copie identique à restaurer sur ce serveur. Chaque synchronisation génère en fait une sauvegarde complète de l'intégralité des données (voir la figure 1-3).
+C'est à ce moment que les systèmes de gestion de version distribués entrent en jeu (DVCSs en anglais pour Distributed Version Control Systems). Dans un DVCS (tel que Git, Mercurial, Bazaar or Darcs), les clients n'extraient plus seulement la dernière version d'un fichier : il dupliquent complètement le dépot. Ainsi, si le serveur disparaît, et si les systèmes collaboraient via ce serveur, n'importe quel dépot d'un des clients peut être copié sur le serveur pour le restaurer. Chaque extraction devient une sauvegarde complète de toutes les données (Cf. Figure 1-3).
-Insert 18333fig0103.png
-Figure 1-3. Diagramme des systèmes distribués de suivi de version.
+Insert 18333fig0103.png
+Figure 1-3. Diagramme de gestion de version de contrôle centralisée.
-En outre, nombre de ces systèmes offre une bonne gestion de multiples dépôts distants avec lesquels travailler, de manière à collaborer avec différents groupes et procéder de différentes manières simultanément au sein d'un même projet. Cela permet la mise en oeuvre de plusieurs méthodes de travail impossible à mettre en place avec des systèmes centralisés, comme des modèles hiérarchiques.
+De plus, un grand nombre de ces systèmes gère particulièrement bien le fait d'avoir plusieurs dépots avec lesquels travailler, vous permettant de collaborer avec différents groupes de personnes de manière différentes simultanément dans le même projet. Celà permet la mise en place de différentes chaînes de traitement qui ne sont pas réalisables avec les systèmes centralisés, tels que les modèles hierarchiques.
-## Une brève histoire de Git ##
+## Une rapide histoire de Git ##
-Comme pour de nombreuses grandes choses de la vie, Git commença par un brin de destruction créatrice et une sauvage controverse. Le noyau Linux est un projet libre qu'on peut qualifier de grande envergure. Durant la majeure partie de la vie du maintien du noyau Linux (1991-2002), les modifications apportées au logiciel circulaient sous formes de corrections (_patches_) et d'archives de fichiers. En 2002, le projet du noyau Linux adopta un SDSV propriétaire nommé BitKeeper.
+Comme de nombreuses choses extraordinaires de la vie, Git est né avec une dose de destruction créative et de controverse houleuse. Le kernel Linux est un projet libre de plutôt grande envergure. Pour la plus grande partie de sa vie (19912002), les modifications étaient transmises sous forme de patchs et d'archives de fichiers. En 2002, le projet du kernel Linux commença à utiliser un DVCS propriétaire appelé BitKeeper.
-En 2005, les relations entre la communauté qui développait le noyau Linux et l'entreprise commerciale qui développait BitKeeper furent brisées et la charte d'utilisation gratuite révoquée. Cela força la communauté qui développe Linux (et en particulier son créateur, Linux Torvalds) à développer son propre outil issu des leçons-apprises en utilisant BitKeeper. Voici résumés quelques-uns des objectifs du nouveau système :
+En 2005, les relations entre la communinauté développant le kernel linux et la société en charge du développement de BitKeeper furent rompues, et le statut de gratuité de l'outil fut révoqué. Celà poussa la communauté du développement de Linux (et plus particulièrement Linus Torvalds, le créateur de Linux) à developper leur propre outil en se basant sur les leçons apprises lors de l'utilisation de BitKeeper. Certains des objectifs du nouveau système étaient les suivants :
-* rapidité
-* architecture simple
-* support natif du développement non-linéaire (des milliers de branches parallèles)
-* entièrement distribué
-* capacité de gérer de gros projets tels le noyau Linux efficacement (vitesse et taille des données)
+* Vitesse
+* Conception simple
+* Support pour les développements non linéaires (milliers de branches parallèles)
+* Complètement distribué
+* Capacité à gérer efficacement des projets d'envergure tels que le kernel Linux (vitesse et compacité des données)
-Depuis sa naissance en 2005, Git a évolué vers la mâturité en restant simple d'utilisation tout en conservant ces qualités initiales. Il est incroyablement rapide, très efficient avec les gros projets, et dispose d'un superbe système de gestion des branches pour le développement non-linéaire (voire chapitre 3).
+Depuis sa naissance en 2005, Git a évolué et mûri vers une utilisation plus simple, tout en retenant ses qualités initiales. Il est incroyablement rapide, il est très efficace pour de grands projets, et il a un système incroyable de gestion de branches pour le développement non linéaire (Cf. Chapitre 3).
-## Les fondements de Git ##
+## Rudiments de Git ##
-Alors, qu'est-ce que Git en deux mots ? C'est une section importante à absorber, parce que si vous comprenez ce qu'est Git et les fondements de son fonctionnement, alors utiliser Git efficacement viendra bien plus aisément pour vous. Durant l'apprentissage de Git, tâchez d'évacuer de votre esprit ce que vous avez appris d'autres SSV, tels Subversion ou Perforce; ce faisant, vous éviterez de subtiles confusion lorsque vous utiliserez l'outil. Git enregistre et approche les données très différemment des autres systèmes, malgré la similarité des interfaces pour l'utilisateur; comprendre ces différences vous permettra d'éviter la confusion lorsque vous l'utiliserez.
+Donc, qu'est-ce que Git en quelques concepts ? Il est important de bien comprendre cette section , parce que si on comprend ce que Git est et les principes sur lesquels il repose, alors utiliser efficacement Git devient simple. Au cours de l'apprentissage de Git, essayer de libérer votre esprit de ce que vous pourriez connaître d'autres VCSs, tels que Subversion et Perforce ; ce faisant, vous vous éviterez de petites confusions à l'utilisation de cet outil. Git sauve et gère l'information très différemment des autres systèmes, même si l'interface utilisateur paraît similaire ; comprendre ses différences vous évitera des confusions à l'utilisation.
-### Sauvegardes au lieu de différences ###
+### Des instantanés, pas des différences ###
-Comment Git "pense" ses données : la différence majeure entre Git et les autres SSV (y compris Subversion et compagnie). Conceptuellement, la plupart des systèmes alternatifs enregistre l'information comme une liste de modifications-par-fichier. Ces systèmes (CVS, Subversion, Perforce, Bazaar, etc.) "pensent" que l'information qu'ils maintiennent s'applique à des lots de fichiers et aux changements effectués dans le temps pour chaque fichier, tel qu'illustré à la figure 1-4.
+La différence majeure entre Git et les autres VCSs (Subversion et autres) réside dans la manière dont Git considère les données. Au niveau conceptuel, la plupart des autres VCSs gèrent l'information comme une liste de modifications de fichiers. Ces systèmes (CVS, Subversion, Perforce, Bazaar, et autres) considèrent l'information qu'il gèrent comme une liste de fichiers et les modifications effectuées sur chaque fichier dans le temps, comme illustré en Figure 1-4.
-Insert 18333fig0104.png
-Figure 1-4. Les autres systèmes tendent à enregistrer les données comme modifications à une version étalon de chaque fichier.
+Insert 18333fig0104.png
+Figure 1-4. Les autres système tendent à sauvegarder l'information comme des modifications sur des fichiers d'origine.
-Git n'approche pas l'enregistrement des données ainsi. A la place, Git conçoit ses données plutôt comme des copies instantanées d'un mini-système-de-fichiers. Chaque fois que vous _committez_, que vous sauvegardez l'état de votre projet dans Git, il prend un instantané de l'état de vos fichiers à ce moment-là et enregistre la référence à cet instantané. Pour plus d'efficacité, si les fichiers n'ont pas changé, Git ne l'enregistre pas de nouveau mais conserve un lien vers la version identique qu'il a déjà enregistrée. La figure 1-5 ressemble à comment Git conçoit ses données.
+Git ne gère pas et ne stocke pas les informations de cette manière. A la place, Git pense ses données plus comme un instantané d'un mini système de fichiers. A chaque fois que vous commitez ou sauvez l'état du projet dan Git, il prend effectivement un instantané du contenu de votre espace de travail à ce moment et sauve une référence à cet instantané. Pour être efficace, si les fichiers n'ont pas changé, Git ne stocke pas le fichier à nouveau, juste une référence vers le fichier original qui n'a pas été modifié. Git pense ses données plus à la manière de la figure 1-5.
-Insert 18333fig0105.png
-Figure 1-5. Git enregistre les données comme instantanés d'un projet dans le temps.
+Insert 18333fig0105.png
+Figure 1-5. Git stocke les données comme des instantanés du projet au cours du temps
-Il s'agit là d'une distinction importante entre Git et les autres SSV. Dans Git, presque tout les aspects du suivi de version que les autres systèmes ont hérité des générations précédentes sont reconsidérés. Cela fait de Git plus un mini-système-de-fichiers sur lequel s'appuient quelques outils d'une puissance incroyable, qu'un simple SSV. Nous reviendrons aux bénéfices de concevoir les données ainsi lorsque nous nous intéresserons aux branches dans le chapitre 3.
+C'est une distinction importante entre Git et quasiment tous les autres VCSs. Celà permet à Git de reconsidérer quasiment tous les aspects de la gestion de version que la plupart des autres système ont copié des générations précédentes. Celà fait quasiment de Git un mini système de fichiers avec des outils incroyablement puissants construit par dessus, plutôt qu'un simple VCS. Nous explorerons les bénéfices qu'il y a à penser les données de cette manière quand nous aborderons la gestion de branches au Chapitre 3.
-### Quasiment toutes les opérations sont locales ###
+### Presque toutes les opération sont locales ###
-La plupart des opérations dans Git nécessite seulement des fichiers et ressources locales pour fonctionner--généralement, il n'y a besoin d'aucune information en provenance d'un autre ordinateur sur votre réseau. Si vous avez l'habitude d'un SCSV où la majorité des opérations souffrent de la latence du réseau, cet aspect de Git vous laissera penser que les dieux de la vitesse lui ont transmis ces pouvoirs. En raison de la présence de l'intégralité de l'historique du projet sur votre disque local, presque toutes les opérations semblent instantanées.
+La plupart des opération sous Git ne nécessite que des fichiers et ressources locales - généralement aucune information venant d'un autre ordinateur du réseau n'est nécessaire. Si vous êtes habitué à un CVCS où toutes les opérations sont ralenties par la latence des échanges réseau, cet aspect de Git vous fera penser que les dieux de la vitesse ont octroyé à Git des pouvoirs divins de vitesse. Comme vous disposez de l'historique complet du projet localement sur votre disque dur, la plupart des opérations semblent instantanées.
-Par exemple, pour accéder à l'historique du projet, Git n'a pas besoin d'interroger un serveur distant : il le lit directement depuis votre base de données locale. Cela signifie que vous visualisez l'historique du projet presque instantanément. Si vous voulez consulter les modifications introduites entre la version courante d'un fichier et sa création un mois auparavant, Git peut accéder à l'état du fichier le mois précédent et effectuer un calcul des différences localement, au lieu d'interroger un serveur distant ou récupérer une version précédente du fichier pour faire le calcul localement.
+Par exemple, pour parcourir l'historique d'un projet, Git n'a pas besoin d'aller la chercher sur un serveur pour vous l'afficher - Il n'a qu'à simplement la lire directement dans votre base de donnée locale. Celà signifie que vous avez quasi-instantanément accès à l'historique du projet.Si vous souhaitez connaître les modifications introduites entre la version actuelle d'un fichier et son état un mois auparavant, Git peut rechercher l'état du fichier un mois auparavant et réaliser le calcul de différence, au lieu d'avoir à demander cette différence à un serveur ou à devoir récupérer l'ancienne version sur le serveur pour calculer la différence localement.
-Cela signifie également qu'il y a très peu de choses que vous ne puissiez faire hors-connexion, ou déconnecté(e) du réseau privé virtuel. Si vous prenez l'avion ou le train et désirez profiter du trajet pour travailler un peu, vous pouvez soumettre vos modifications avec bonheur jusqu'à ce que vous puissiez vous connecter pour synchroniser vos données. Une fois à la maison, si vous ne parvenez pas à restaurer la connexion vers votre réseau privé virtuel, vous pouvez tout de même travailler. Avec d'autres systèmes, ces situations s'avèrent impossibles ou très difficiles à mettre en oeuvre. Dans Perforce, par exemple, vous ne pouvez pas faire grand chose sans une connexion au serveur ; et dans Subversion ou CVS, vous pouvez modifier des fichiers, mais vous ne pouvez soumettre aucune modification (parce que votre base de données est déconnectée). Cela peut sembler anodin, mais vous pourriez être surpris(e) de la grande différence que cela peut constituer.
+Celà signifie aussi qu'il y a très peu de choses que vous ne puissiez réaliser si vous n'êtes pas connecté ou hors VPN. Si vous voyagez en train ou en avion et voulez avancer votre travail, vous pouvez continuer à gérer vos versions sans soucis en attendant de pouvoir de nouveau vous connecter pour partager votre travail. Si vous êtes chez vous et ne pouvez avoir une liaison VPN avec votre entreprise, vous pouvez tout de même travailler. Pour de nombreux autres systèmes, faire de même est au choix impossible ou vraiment très contraignant. Avec Perforce par éxemple, vous ne pouvez pas faire grand'chose tant que vous n'êtes pas connecté au serveur de version ; et avec Subversion ou CVS, vous pouvez éditer les fichiers, mais vous ne pourrez pas gérer de version dans votre base de données (car celle-ci est sur le serveur non accessible). Celà peut sembler peu important a priori, mais vous seriez étonné de découvrir quelle grande différence ça peut faire à l'usage.
-### Git possède l'intégrité ###
+### Git gère l'intégrité ###
-Tout dans Git est soumis à une somme de contrôle, qui deviendra la référence, avant d'être enregistré. Cela veut dire qu'il est impossible de modifier le contenu d'aucun fichier ou répertoire sans que Git ne le sache. Cette fonctionnalité est intégrée dans Git au plus bas niveau aussi bien que dans sa philosophie. Vous ne pouvez perdre de l'information pendant les transferts, ni obtenir un fichier corrompu sans que Git ne puisse le détecter.
+Dans Git,tout est vérifié par somme de contrôle avant d'être stocké et par la suite la somme de contrôle, signature unique, sert de référence. Celà signifie qu'il est impossible de modifier le contenu d'un fichier ou d'un répertoire sans que Git ne s'en aperçoive. Cette fonctionnalité est ancrée dans les fondations de Git et fait partie intégrante de sa philosphie. Vous ne pouvez pas perdre des données en cours de transfert ou corrompre un fichier sans que Git ne le détecte immédiatement.
-Git utilise une signature SHA-1 pour les sommes de contrôle. Il s'agit d'une chaîne de 40 caractères hexadécimaux (de 0 à 9 et de A à F), une empreinte unique issue du contenu du fichier ou de la structure des répertoires dans Git. Une empreinte SHA-1 ressemble à ceci :
+Le mécanisme que Git utilise pour réaliser les sommes de contrôle est appelé SHA-1. C'est une chaîne de caractères composée de 40 caractères héxadécimaux (de '0' à '9' et de 'a' à 'f') calculée en fonction du contenu du fichier ou de la structure du répertoire considéré. Une signature SHA-1 ressembe à ceci :
24b9da6552252987aa493b52f8696cd6d3b00373
-Vous verrez ce genre d'empreintes un peu partout dans Git car il les utilise partout. En fait, Git enregistre tout non par nom de fichier, mais dans une base de données addressable par la signature SHA-1 des contenus.
+Vous trouverez ces valeurs à peu près partout dans Git car il les utilise pour tout. En fait, Git stocke tout non pas avec des noms de fichier, mais dans la base de données Git indéxée par ces valeurs.
-### Git ne fait (presque) qu'ajouter des données ###
+### Généralement, Git ne fait qu'ajouter des données ###
-Lorsque vous effectuez des opérations dans Git, presque toutes ne font qu'ajouter des données dans la base de données de Git. Il est très difficile de forcer le système à faire quelque chose qu'on ne puisse défaire ou à effacer des données d'un quelconque manière. Comme dans tous les SSV, vous pouvez perdre ou casser des modifications que vous n'avez pas encore consignées ; mais une fois que vous avez consigné une image de vos changements dans Git, il devient très difficile de les perdre, d'autant plus si vous synchronisez régulièrement votre dépôt vers un autre dépôt.
+Quand vous réalisez des actions dans Git, la quasi-totalité d'entre elles ne font qu'ajouter des données dans la base de données de Git. Il est très difficile de faire réaliser au système des actions qui ne soient pas réversibles ou de lui faire effacer des données d'une quelconque manière. Par contre, comme dans la plupart des systèmes de gestion de version, vous pouvez perdre ou corrompre des modifications qui n'ont pas encore été entrées en base ; mais dès que vous avez commité un instantané dans Git, il est très difficile de le perdre, spécialement si en plus vous synchronisez votre base de données locale avec un dépot distant.
-Cela rend Git agréable à utiliser parce que nous savons que nous pouvons expérimenter sans danger de détruire le projet. Pour une vision plus approfondie de la manière dont Git enregistre ses données, et les moyens de récupérer des données qui semblent perdues, voir "Sous le couvercle" dans la chapitre 9.
+Celà fait de l'usage de Git un vrai plaisir, car on peut expérimenter sans danger de casser définitivement notre projet. Pour une information plus approfondie de la manière dont Git stocke ses données et de comment récupérer des données qui pourraient sembler perdues, référez-vous au chapitre 9 "Sous le capot".
### Les trois états ###
-A présent, prêtez attention. Il s'agit de la chose principale à retenir concernant Git si vous voulez que le reste de votre apprentissage se passe sans encombre. Git possède trois états principaux dans lesquels vos fichiers peuvent se trouver : consigné, modifié ou en attente. Consigné signifie que les données sont enregistrées, à l'abri, dans votre base de données locale. Modifié veut dire que des changements ont eu lieu, mais qu'ils ne sont pas encore consignés. En attente implique que vous avez marqué un fichier modifié dans sa version courante pour qu'il intègre la prochaine image consignée.
+Ici, il faut être attentif. Il est primordial de se souvenir de ce qui suit si vous souhaitez que le reste de votre apprentissage s'effectue sans difficulté. Git gère trois états dans lequel les fichiers peuvent résider : commité, modifié et indexé. Commité signifie que les données sont stockées en sécurité dans votre base de données locale. Modifié signifie que vous avez modifié le fichier mais qu'il n'a pas encore été commité en base. Indéxé signifie que vous avez marqué un fichier modifié dans sa version actuelle pour qu'il fasse partie du prochain instantané du projet.
-Cela nous amène aux trois principales sections d'un projet Git : le répertoire Git, le répertoire de travail et la zone d'attente.
+Ceci nous mène aux trois sections principales d'un projet Git : le répertoire Git, le répertoire de travail et la zone d'index.
-Insert 18333fig0106.png
-Figure 1-6. Le répertoire de travail, zone d'attente et le répertoire Git.
+Insert 18333fig0106.png
+Figure 1-6. Répertoire de travail, zone d'index et répertoire Git.
-Le répertoire Git est l'endroit ou Git enregistre les méta-données et la base de données d'objets pour votre projet. C'est la partie la plus importante de Git, et c'est ce qui est copié lors d'une opération de clonage du dépôt depuis une autre machine.
+Le répertoire Git est l'endroit Git stocke les métadonnées et la base de données des objets de votre projet. C'est la partie la plus importante de Git, et c'est ce qui est copié lorsque vous clonez une dépot depuis un autre ordinateur.
-Le répertoire de travail est un retrait unique d'une version du projet. Ces fichiers sont retirés de la base de données compressée dans le répertoire Git et placés sur le disque pour être utilisés ou modifiés.
+Le répertoire de travail est une extraction unique d'un version du projet. Ces fichiers sont extraits depuis la base de données compressée dans le répertoire Git et placés sur le disque pour pouvoir être utilisés ou modifiés.
-La zone d'attente est un simple fichier, généralement placé dans le répertoire Git, qui contient l'information relative aux modifications qui intègreront la prochaine consignation. On l'appelle parfois l'index, mais l'appellation courante, qui devient le standard, est la zone d'attente.
+La zone d'index est un simple fichier, généralement situé sans le répertoire Git, qui stocke les informations concernant ce qui fera partie du prochain instantané.
-L'usage fondamental de Git peut se décrire ainsi :
+L'utilisation standard de Git se passe comme suit :
-1. Vous modifiez des fichiers dans votre répertoire de travail.
-2. Vous mettez les fichiers en attente, en ajoutant leur image à la zone d'attente.
-3. Vous consignez les fichiers, ce qui prend un instantané des fichiers en attente et l'enregistre définitivement dans votre répertoire Git.
+1. Vous modifiez des fichiers dans votre répertoire de travail
+2. Vous indéxez les fichiers modifiés, ce qui ajoute des instantanés de ces fichiers dans la zone d'index
+3. Vous réalisez un commit, ce qui a pour effet de basculer les instantanés des fichiers de l'index dans la base de donnée du répertoire Git.
-Si une version particulière d'un fichier est présente dans le répertoire Git, elle est considérée comme consignée. Si elle est modifiée mais présente dans la zone d'attente, elle est en attente. Et si elle a été modifiée depuis le dernier retrait, mais n'est pas encore en attente, alors elle est considérée comme modifiée. Dans le chapitre 2, vous en apprendrez plus sur ces états et comment vous pouvez en tirez avantage ou éviter la zone d'attente entièrement.
+Si une version particulière d'un fichier est dans le répertoire Git, il est considéré comme commité. S'il est modifié mais a été ajouté dans la zone d'index, il est indéxé. S'il a été modifié depuis le dernier instantané mais n'a pas été indéxé, il est modifié. Dans le chapitre 2, vous en apprendrez plus sur ces états et commment vous pouvez en tirer parti ou complètement les occulter.
-## Installing Git ##
+## Installation de Git ##
-Let’s get into using some Git. First things first—you have to install it. You can get it a number of ways; the two major ones are to install it from source or to install an existing package for your platform.
+Commençons donc à utiliser Git. La première des choses est de l'installer. Vous pouvez l'obtenir par de nombreuses manières ; les deux principales sont de l'installer à partir des sources ou d'installer un paquetage éxistant sur votre plateforme.
-### Installing from Source ###
+### Installation depuis les sources ###
-If you can, it’s generally useful to install Git from source, because you’ll get the most recent version. Each version of Git tends to include useful UI enhancements, so getting the latest version is often the best route if you feel comfortable compiling software from source. It is also the case that many Linux distributions contain very old packages; so unless you’re on a very up-to-date distro or are using backports, installing from source may be the best bet.
+Si vous le pouvez, il est généralement mieux d'installer Git à partir des sources, car vous obtiendrez la version la plus récente. Chaque nouvelle version de Git tend à inclure des améliorations utiles de l'interface utilisateur, donc récupérer la toute dernière version est souvent le mieux si vous savez compiler des logiciels à partir des sources. Comme la plupart du temps les distributions contiennent des version très anciennes de logiciels, à moins que vous ne travailliez sur une distribution très récente ou que vous n'utilisiez des backports, une installation à partir des sources est gage de meilleur fonctionnement.
-To install Git, you need to have the following libraries that Git depends on: curl, zlib, openssl, expat, and libiconv. For example, if you’re on a system that has yum (such as Fedora) or apt-get (such as a Debian based system), you can use one of these commands to install all of the dependencies:
+Pour installer Git, vous avez besoin des bibliothèques suivantes : curl, zlib, openssl, expat, libiconv. Par éxemple, si vous avez un système d'exploitation qui utilise yum (tel que Fedora) ou apt-get (tel qu'un système basé sur Debian), vous pouvez utiliser les commandes suivantes pour installer les dépendances :
$ yum install curl-devel expat-devel gettext-devel \
openssl-devel zlib-devel
$ apt-get install libcurl4-gnutls-dev libexpat1-dev gettext \
libz-dev
-
-When you have all the necessary dependencies, you can go ahead and grab the latest snapshot from the Git web site:
+
+Quand vous avez toutes les dépendances nécessaires, vous pouvez poursuivre et télécharger la dernière version de Git depuis le site :
http://git-scm.com/download
-
-Then, compile and install:
+
+Puis, compiler et installer
$ tar -zxf git-1.6.0.5.tar.gz
$ cd git-1.6.0.5
$ make prefix=/usr/local all
$ sudo make prefix=/usr/local install
-After this is done, you can also get Git via Git itself for updates:
+Après ceci, vous pouvez obtenir Git par Git lui-même pour le mises à jour :
$ git clone git://git.kernel.org/pub/scm/git/git.git
+
+### Installation sur Linux ###
-### Installing on Linux ###
-
-If you want to install Git on Linux via a binary installer, you can generally do so through the basic package-management tool that comes with your distribution. If you’re on Fedora, you can use yum:
+Si vous souhaitez installer Git sur Linux via un installeur d'application, vous pouvez généralement le faire via le système de gestion de paquetage de base fourni avec votre distribution. Si vous êtes sur Fedora, vous pouvez utiliser yum :
$ yum install git-core
-Or if you’re on a Debian-based distribution like Ubuntu, try apt-get:
+Si vous êtes sur un système basé sur Debian, tel qu'Ubuntu, essayez apt-get :
$ apt-get install git-core
-### Installing on Mac ###
+### Installation sur Mac ###
-There are two easy ways to install Git on a Mac. The easiest is to use the graphical Git installer, which you can download from the Google Code page (see Figure 1-7):
+Il y a deux moyens simples d'installer Git sur Mac. Le plus simple et d'utiliser l'installateur graphique de Git que vous pouvez télécharger depuis les pages Google Code (Cf. Figure 1-7) :
http://code.google.com/p/git-osx-installer
-Insert 18333fig0107.png
-Figure 1-7. Git OS X installer.
+Insert 18333fig0107.png
+Figure 1-7. Installateur OS X de Git.
-The other major way is to install Git via MacPorts (`http://www.macports.org`). If you have MacPorts installed, install Git via
+L'autre méthode consiste à installer Git par les MacPorts ((`http://www.macports.org`). Si vous avez installé MacPorts, installez Git par :
$ sudo port install git-core +svn +doc +bash_completion +gitweb
-You don’t have to add all the extras, but you’ll probably want to include +svn in case you ever have to use Git with Subversion repositories (see Chapter 8).
+Vous n'avez pas à ajouter tous les extras, mais vous souhaiterez surement inclure +svn dans le cas où vous chercheriez à utiliser Git avec des dépots Subversion (voir Chapitre 8).
-### Installing on Windows ###
+### Installation sur Windows ###
-Installing Git on Windows is very easy. The msysGit project has one of the easier installation procedures. Simply download the installer exe file from the Google Code page, and run it:
+Installer Git sur Windows est très facile. Le projet msysGit fournit une des procédures d'installation les plus faciles. Téléchargez simplement le fichier exe d'installateur depuis la page Google Code, et lancez-le :
http://code.google.com/p/msysgit
-After it’s installed, you have both a command-line version (including an SSH client that will come in handy later) and the standard GUI.
+Après son installation, vous avez à la fois la version en ligne de commande (avec un client SSH utile pour la suite) ou l'interface graphique standard.
-## First-Time Git Setup ##
+## Paramétrage à la première utilisation de Git ##
-Now that you have Git on your system, you’ll want to do a few things to customize your Git environment. You should have to do these things only once; they’ll stick around between upgrades. You can also change them at any time by running through the commands again.
+Maintenant que vous avez Git installé sur votre système, vous voudrez personnaliser votre environnement Git. Vous ne devriez avoir à réaliser ces réglages qu'une seule fois ; elles persisteront lors des mises à jour. Vous pouvez aussi les changer à tout instant en relançant les mêmes commandes.
-Git comes with a tool called git config that lets you get and set configuration variables that control all aspects of how Git looks and operates. These variables can be stored in three different places:
+Git contient un outil appelé git config pour vous permettre de voir et modifier les variables de configuration qui contrôlent tous les aspects de l'apparence et du comportement de Git. Ces variables peuvent être stockées dans trois endroits différents :
-* `/etc/gitconfig` file: Contains values for every user on the system and all their repositories. If you pass the option` --system` to `git config`, it reads and writes from this file specifically.
-* `~/.gitconfig` file: Specific to your user. You can make Git read and write to this file specifically by passing the `--global` option.
-* config file in the git directory (that is, `.git/config`) of whatever repository you’re currently using: Specific to that single repository. Each level overrides values in the previous level, so values in `.git/config` trump those in `/etc/gitconfig`.
+* Fichier `/etc/gitconfig` : Contient les valeurs pour tous les utilisateurs et tous les dépots du système. Si vous passez l'option `--system` à `git config`, il lit et écrit ce fichier spécifiquement.
+* Fichier `~/.gitconfig` : Spécifique à votre utilisateur. Vous pouvez forcer Git à lire et écrire ce fichier en passant l'option `--global`.
+* Fichier `config` dans le répertoire Git (c'est à dire, `.git/config`) du dépot en cours d'utilisation : spécifique au seul dépot en cours. Chaque niveau surcharge le niveau précédent, donc les valeurs dans `.git/config` surchargent celles de `/etc/gitconfig`.
-On Windows systems, Git looks for the `.gitconfig` file in the `$HOME` directory (`C:\Documents and Settings\$USER` for most people). It also still looks for /etc/gitconfig, although it’s relative to the MSys root, which is wherever you decide to install Git on your Windows system when you run the installer.
+Sur les systèmes Windows, Git recherche le fichier `.gitconfig` dans le répertoire `$HOME` (`C:\Documents and Settings\$USER` la plupart du temps). Il recherche tout de même `/etc/gitconfig`, bien qu'il soit relatif à la racine MSys, qui se trouve où vous aurez décidé d'installer Git sur votre système Windows.
-### Your Identity ###
+### Votre identité ###
-The first thing you should do when you install Git is to set your user name and e-mail address. This is important because every Git commit uses this information, and it’s immutably baked into the commits you pass around:
+La première chose à faire après l'installation de Git est de renseigner votre nom et votre adress e-mail. C'est important car tous les commits Git utilisent cette information et elle est indélébile dans tous les commits que vous pourrez manipuler :
$ git config --global user.name "John Doe"
$ git config --global user.email johndoe@example.com
-Again, you need to do this only once if you pass the `--global` option, because then Git will always use that information for anything you do on that system. If you want to override this with a different name or e-mail address for specific projects, you can run the command without the `--global` option when you’re in that project.
+Encore une fois, cette étape n'est nécessaire qu'une fois si vous passez l'option `--global`, parce que Git utilisera toujours cette information pour tout ce que votre utilisateur fera sur ce système. Si vous souhaitez surcharger ces valeurs avec un nom ou une adresse e-mail différents pour un projet spécifique, vous pouvez lancer ces commandes sans option `--global` lorsque vous êtes dans ce projet.
-### Your Editor ###
+### Votre éditeur de texte ###
-Now that your identity is set up, you can configure the default text editor that will be used when Git needs you to type in a message. By default, Git uses your system’s default editor, which is generally Vi or Vim. If you want to use a different text editor, such as Emacs, you can do the following:
+À présent que votre identité est renseignée, vous pouvez configurer l'éditeur de texte qui sera utilisé par défaut quand Git vous enjoint à taper un message. Par défaut, Git utilise votre éditeur par défaut au niveau système, qui est généralement Vi ou Vim. Si vous souhaitez utiliser un éditeur de texte différent, comme Emacs, vous pouvez faire ce qui suit :
$ git config --global core.editor emacs
+
+### Votre outil de diff ###
-### Your Diff Tool ###
-
-Another useful option you may want to configure is the default diff tool to use to resolve merge conflicts. Say you want to use vimdiff:
+Une autre option utile est le paramétrage de l'outil de diff à utiliser pour la résolution des conflits de fusion. Supposons que vous souhaitiez utiliser vimdiff :
$ git config --global merge.tool vimdiff
-Git accepts kdiff3, tkdiff, meld, xxdiff, emerge, vimdiff, gvimdiff, ecmerge, and opendiff as valid merge tools. You can also set up a custom tool; see Chapter 7 for more information about doing that.
+Git accepte kdiff3, tkdiff, meld, xxdiff, emerge, vimdiff, gvimdiff, ecmerge, et opendiff comme outils valides de fusion. Vous pouvez aussi paramétrer un outil personnalisé ; référez-vous au chapitre 7 pour plus d'information sur cette procédure.
-### Checking Your Settings ###
+### Vérifier vos paramètres ###
-If you want to check your settings, you can use the `git config --list` command to list all the settings Git can find at that point:
+Si vous souhaitez vérifier vos réglages, vous pouvez utiliser la commande `git config --list` pour lister tous les réglages que Git a pu trouver jusqu'ici :
$ git config --list
user.name=Scott Chacon
@@ -230,28 +230,28 @@ If you want to check your settings, you can use the `git config --list` command
color.diff=auto
...
-You may see keys more than once, because Git reads the same key from different files (`/etc/gitconfig` and `~/.gitconfig`, for example). In this case, Git uses the last value for each unique key it sees.
+Vous pourrez voir certains paramètres apparaître plusieurs fois, car Git lit les mêmes paramètres depuis plusieurs fichiers (`/etc/gitconfig` et `~/.gitconfig`, par exemple). Git utilise la dernière valeur pour chaque paramètre.
-You can also check what Git thinks a specific key’s value is by typing `git config {key}`:
+Vous pouvez aussi vérifier la valeur particulière utilisée d'un paramètre en tapant `git config {paramètre}`:
$ git config user.name
Scott Chacon
-## Getting Help ##
+## Obtenir de l'aide ##
-If you ever need help while using Git, there are three ways to get the manual page (manpage) help for any of the Git commands:
+Si vous avez besoin d'aide pour utiliser Git, il y a trois moyens d'obtenir les pages de manuel (manpage) pour toutes les commandes de Git :
- $ git help <verb>
+ $ git help <verbe>
$ git <verb> --help
- $ man git-<verb>
+ $ man git-<verbe>
-For example, you can get the manpage help for the config command by running
+Par exemple, vous pouvez obtenir la page de manuel pour la commande config en lançant :
$ git help config
-These commands are nice because you can access them anywhere, even offline.
-If the manpages and this book aren’t enough and you need in-person help, you can try the `#git` or `#github` channel on the Freenode IRC server (irc.freenode.net). These channels are regularly filled with hundreds of people who are all very knowledgeable about Git and are often willing to help.
+Ces commandes sont vraiment sympathiques car vous pouvez y accéder depuis partout, y compris hors connexion.
+Si les manpages et ce livre ne sont pas suffisants, vous pouvez essayer les canaux `#git` ou `#github` sur le serveur IRC Freenode (irc.freenode.net). Ces canaux sont régulièrement peuplés de centaines de personnes qui ont une bonne connaissance de Git et sont souvent prêtes à aider.
-## Summary ##
+## Résumé ##
-You should have a basic understanding of what Git is and how it’s different from the CVCS you may have been using. You should also now have a working version of Git on your system that’s set up with your personal identity. It’s now time to learn some Git basics.
+Vous devriez avoir à présent une compréhension initiale de ce que Git est et en quoi il est différent des CVCS que vous pourriez déjà avoir utilisés. Vous devriez aussi avoir une version de Git en état de fonctionnement sur votre système, paramétrée avec votre identité. Il est temps d'apprendre les bases d'utilisation de Git.
View
1,121 fr/02-git-basics/01-chapter2.markdown
@@ -0,0 +1,1121 @@
+# Git Basics #
+
+If you can read only one chapter to get going with Git, this is it. This chapter covers every basic command you need to do the vast majority of the things you’ll eventually spend your time doing with Git. By the end of the chapter, you should be able to configure and initialize a repository, begin and stop tracking files, and stage and commit changes. We’ll also show you how to set up Git to ignore certain files and file patterns, how to undo mistakes quickly and easily, how to browse the history of your project and view changes between commits, and how to push and pull from remote repositories.
+
+## Getting a Git Repository ##
+
+You can get a Git project using two main approaches. The first takes an existing project or directory and imports it into Git. The second clones an existing Git repository from another server.
+
+### Initializing a Repository in an Existing Directory ###
+
+If you’re starting to track an existing project in Git, you need to go to the project’s directory and type
+
+ $ git init
+
+This creates a new subdirectory named .git that contains all of your necessary repository files — a Git repository skeleton. At this point, nothing in your project is tracked yet. (See Chapter 9 for more information about exactly what files are contained in the `.git` directory you just created.)
+
+If you want to start version-controlling existing files (as opposed to an empty directory), you should probably begin tracking those files and do an initial commit. You can accomplish that with a few git add commands that specify the files you want to track, followed by a commit:
+
+ $ git add *.c
+ $ git add README
+ $ git commit –m 'initial project version'
+
+We’ll go over what these commands do in just a minute. At this point, you have a Git repository with tracked files and an initial commit.
+
+### Cloning an Existing Repository ###
+
+If you want to get a copy of an existing Git repository — for example, a project you’d like to contribute to — the command you need is git clone. If you’re familiar with other VCS systems such as Subversion, you’ll notice that the command is clone and not checkout. This is an important distinction — Git receives a copy of nearly all data that the server has. Every version of every file for the history of the project is pulled down when you run `git clone`. In fact, if your server disk gets corrupted, you can use any of the clones on any client to set the server back to the state it was in when it was cloned (you may lose some server-side hooks and such, but all the versioned data would be there—see Chapter 4 for more details).
+
+You clone a repository with `git clone [url]`. For example, if you want to clone the Ruby Git library called Grit, you can do so like this:
+
+ $ git clone git://github.com/schacon/grit.git
+
+That creates a directory named "grit", initializes a `.git` directory inside it, pulls down all the data for that repository, and checks out a working copy of the latest version. If you go into the new `grit` directory, you’ll see the project files in there, ready to be worked on or used. If you want to clone the repository into a directory named something other than grit, you can specify that as the next command-line option:
+
+ $ git clone git://github.com/schacon/grit.git mygrit
+
+That command does the same thing as the previous one, but the target directory is called mygrit.
+
+Git has a number of different transfer protocols you can use. The previous example uses the `git://` protocol, but you may also see `http(s)://` or `user@server:/path.git`, which uses the SSH transfer protocol. Chapter 4 will introduce all of the available options the server can set up to access your Git repository and the pros and cons of each.
+
+## Recording Changes to the Repository ##
+
+You have a bona fide Git repository and a checkout or working copy of the files for that project. You need to make some changes and commit snapshots of those changes into your repository each time the project reaches a state you want to record.
+
+Remember that each file in your working directory can be in one of two states: tracked or untracked. Tracked files are files that were in the last snapshot; they can be unmodified, modified, or staged. Untracked files are everything else - any files in your working directory that were not in your last snapshot and are not in your staging area. When you first clone a repository, all of your files will be tracked and unmodified because you just checked them out and haven’t edited anything.
+
+As you edit files, Git sees them as modified, because you’ve changed them since your last commit. You stage these modified files and then commit all your staged changes, and the cycle repeats. This lifecycle is illustrated in Figure 2-1.
+
+Insert 18333fig0201.png
+Figure 2-1. The lifecycle of the status of your files.
+
+### Checking the Status of Your Files ###
+
+The main tool you use to determine which files are in which state is the git status command. If you run this command directly after a clone, you should see something like this:
+
+ $ git status
+ # On branch master
+ nothing to commit (working directory clean)
+
+This means you have a clean working directory—in other words, there are no tracked and modified files. Git also doesn’t see any untracked files, or they would be listed here. Finally, the command tells you which branch you’re on. For now, that is always master, which is the default; you won’t worry about it here. The next chapter will go over branches and references in detail.
+
+Let’s say you add a new file to your project, a simple README file. If the file didn’t exist before, and you run `git status`, you see your untracked file like so:
+
+ $ vim README
+ $ git status
+ # On branch master
+ # Untracked files:
+ # (use "git add <file>..." to include in what will be committed)
+ #
+ # README
+ nothing added to commit but untracked files present (use "git add" to track)
+
+You can see that your new README file is untracked, because it’s under the “Untracked files” heading in your status output. Untracked basically means that Git sees a file you didn’t have in the previous snapshot (commit); Git won’t start including it in your commit snapshots until you explicitly tell it to do so. It does this so you don’t accidentally begin including generated binary files or other files that you did not mean to include. You do want to start including README, so let’s start tracking the file.
+
+### Tracking New Files ###
+
+In order to begin tracking a new file, you use the command `git add`. To begin tracking the README file, you can run this:
+
+ $ git add README
+
+If you run your status command again, you can see that your README file is now tracked and staged:
+
+ $ git status
+ # On branch master
+ # Changes to be committed:
+ # (use "git reset HEAD <file>..." to unstage)
+ #
+ # new file: README
+ #
+
+You can tell that it’s staged because it’s under the “Changes to be committed” heading. If you commit at this point, the version of the file at the time you ran git add is what will be in the historical snapshot. You may recall that when you ran git init earlier, you then ran git add (files) — that was to begin tracking files in your directory. The git add command takes a path name for either a file or a directory; if it’s a directory, the command adds all the files in that directory recursively.
+
+### Staging Modified Files ###
+
+Let’s change a file that was already tracked. If you change a previously tracked file called `benchmarks.rb` and then run your `status` command again, you get something that looks like this:
+
+ $ git status
+ # On branch master
+ # Changes to be committed:
+ # (use "git reset HEAD <file>..." to unstage)
+ #
+ # new file: README
+ #
+ # Changed but not updated:
+ # (use "git add <file>..." to update what will be committed)
+ #
+ # modified: benchmarks.rb
+ #
+
+The benchmarks.rb file appears under a section named “Changed but not updated” — which means that a file that is tracked has been modified in the working directory but not yet staged. To stage it, you run the `git add` command (it’s a multipurpose command — you use it to begin tracking new files, to stage files, and to do other things like marking merge-conflicted files as resolved). Let’s run `git add` now to stage the benchmarks.rb file, and then run `git status` again:
+
+ $ git add benchmarks.rb
+ $ git status
+ # On branch master
+ # Changes to be committed:
+ # (use "git reset HEAD <file>..." to unstage)
+ #
+ # new file: README
+ # modified: benchmarks.rb
+ #
+
+Both files are staged and will go into your next commit. At this point, suppose you remember one little change that you want to make in benchmarks.rb before you commit it. You open it again and make that change, and you’re ready to commit. However, let’s run `git status` one more time:
+
+ $ vim benchmarks.rb
+ $ git status
+ # On branch master
+ # Changes to be committed:
+ # (use "git reset HEAD <file>..." to unstage)
+ #
+ # new file: README
+ # modified: benchmarks.rb
+ #
+ # Changed but not updated:
+ # (use "git add <file>..." to update what will be committed)
+ #
+ # modified: benchmarks.rb
+ #
+
+What the heck? Now benchmarks.rb is listed as both staged and unstaged. How is that possible? It turns out that Git stages a file exactly as it is when you run the git add command. If you commit now, the version of benchmarks.rb as it was when you last ran the git add command is how it will go into the commit, not the version of the file as it looks in your working directory when you run git commit. If you modify a file after you run `git add`, you have to run `git add` again to stage the latest version of the file:
+
+ $ git add benchmarks.rb
+ $ git status
+ # On branch master
+ # Changes to be committed:
+ # (use "git reset HEAD <file>..." to unstage)
+ #
+ # new file: README
+ # modified: benchmarks.rb
+ #
+
+### Ignoring Files ###
+
+Often, you’ll have a class of files that you don’t want Git to automatically add or even show you as being untracked. These are generally automatically generated files such as log files or files produced by your build system. In such cases, you can create a file listing patterns to match them named .gitignore. Here is an example .gitignore file:
+
+ $ cat .gitignore
+ *.[oa]
+ *~
+
+The first line tells Git to ignore any files ending in .o or .a — object and archive files that may be the product of building your code. The second line tells Git to ignore all files that end with a tilde (`~`), which is used by many text editors such as Emacs to mark temporary files. You may also include a log, tmp, or pid directory; automatically generated documentation; and so on. Setting up a .gitignore file before you get going is generally a good idea so you don’t accidentally commit files that you really don’t want in your Git repository.
+
+The rules for the patterns you can put in the .gitignore file are as follows:
+
+* Blank lines or lines starting with # are ignored.
+* Standard glob patterns work.
+* You can end patterns with a forward slash (`/`) to specify a directory.
+* You can negate a pattern by starting it with an exclamation point (`!`).
+
+Glob patterns are like simplified regular expressions that shells use. An asterisk (`*`) matches zero or more characters; `[abc]` matches any character inside the brackets (in this case a, b, or c); a question mark (`?`) matches a single character; and brackets enclosing characters separated by a hyphen(`[0-9]`) matches any character between them (in this case 0 through 9) .
+
+Here is another example .gitignore file:
+
+ # a comment – this is ignored
+ *.a # no .a files
+ !lib.a # but do track lib.a, even though you're ignoring .a files above
+ /TODO # only ignore the root TODO file, not subdir/TODO
+ build/ # ignore all files in the build/ directory
+ doc/*.txt # ignore doc/notes.txt, but not doc/server/arch.txt
+
+### Viewing Your Staged and Unstaged Changes ###
+
+If the `git status` command is too vague for you — you want to know exactly what you changed, not just which files were changed — you can use the `git diff` command. We’ll cover `git diff` in more detail later; but you’ll probably use it most often to answer these two questions: What have you changed but not yet staged? And what have you staged that you are about to commit? Although `git status` answers those questions very generally, `git diff` shows you the exact lines added and removed — the patch, as it were.
+
+Let’s say you edit and stage the README file again and then edit the benchmarks.rb file without staging it. If you run your `status` command, you once again see something like this:
+
+ $ git status
+ # On branch master
+ # Changes to be committed:
+ # (use "git reset HEAD <file>..." to unstage)
+ #
+ # new file: README
+ #
+ # Changed but not updated:
+ # (use "git add <file>..." to update what will be committed)
+ #
+ # modified: benchmarks.rb
+ #
+
+To see what you’ve changed but not yet staged, type `git diff` with no other arguments:
+
+ $ git diff
+ diff --git a/benchmarks.rb b/benchmarks.rb
+ index 3cb747f..da65585 100644
+ --- a/benchmarks.rb
+ +++ b/benchmarks.rb
+ @@ -36,6 +36,10 @@ def main
+ @commit.parents[0].parents[0].parents[0]
+ end
+
+ + run_code(x, 'commits 1') do
+ + git.commits.size
+ + end
+ +
+ run_code(x, 'commits 2') do
+ log = git.commits('master', 15)
+ log.size
+
+That command compares what is in your working directory with what is in your staging area. The result tells you the changes you’ve made that you haven’t yet staged.
+
+If you want to see what you’ve staged that will go into your next commit, you can use `git diff –-cached`. (In Git versions 1.6.1 and later, you can also use `git diff –-staged`, which may be easier to remember.) This command compares your staged changes to your last commit:
+
+ $ git diff --cached
+ diff --git a/README b/README
+ new file mode 100644
+ index 0000000..03902a1
+ --- /dev/null
+ +++ b/README2
+ @@ -0,0 +1,5 @@
+ +grit
+ + by Tom Preston-Werner, Chris Wanstrath
+ + http://github.com/mojombo/grit
+ +
+ +Grit is a Ruby library for extracting information from a Git repository
+
+It’s important to note that `git diff` by itself doesn’t show all changes made since your last commit — only changes that are still unstaged. This can be confusing, because if you’ve staged all of your changes, `git diff` will give you no output.
+
+For another example, if you stage the benchmarks.rb file and then edit it, you can use `git diff` to see the changes in the file that are staged and the changes that are unstaged:
+
+ $ git add benchmarks.rb
+ $ echo '# test line' >> benchmarks.rb
+ $ git status
+ # On branch master
+ #
+ # Changes to be committed:
+ #
+ # modified: benchmarks.rb
+ #
+ # Changed but not updated:
+ #
+ # modified: benchmarks.rb
+ #
+
+Now you can use `git diff` to see what is still unstaged
+
+ $ git diff
+ diff --git a/benchmarks.rb b/benchmarks.rb
+ index e445e28..86b2f7c 100644
+ --- a/benchmarks.rb
+ +++ b/benchmarks.rb
+ @@ -127,3 +127,4 @@ end
+ main()
+
+ ##pp Grit::GitRuby.cache_client.stats
+ +# test line
+
+and `git diff --cached` to see what you’ve staged so far:
+
+ $ git diff --cached
+ diff --git a/benchmarks.rb b/benchmarks.rb
+ index 3cb747f..e445e28 100644
+ --- a/benchmarks.rb
+ +++ b/benchmarks.rb
+ @@ -36,6 +36,10 @@ def main
+ @commit.parents[0].parents[0].parents[0]
+ end
+
+ + run_code(x, 'commits 1') do
+ + git.commits.size
+ + end
+ +
+ run_code(x, 'commits 2') do
+ log = git.commits('master', 15)
+ log.size
+
+### Committing Your Changes ###
+
+Now that your staging area is set up the way you want it, you can commit your changes. Remember that anything that is still unstaged — any files you have created or modified that you haven’t run `git add` on since you edited them — won’t go into this commit. They will stay as modified files on your disk.
+In this case, the last time you ran `git status`, you saw that everything was staged, so you’re ready to commit your changes. The simplest way to commit is to type `git commit`:
+
+ $ git commit
+
+Doing so launches your editor of choice. (This is set by your shell’s `$EDITOR` environment variable — usually vim or emacs, although you can configure it with whatever you want using the `git config --global core.editor` command as you saw in Chapter 1).
+
+The editor displays the following text (this example is a Vim screen):
+
+ # Please enter the commit message for your changes. Lines starting
+ # with '#' will be ignored, and an empty message aborts the commit.
+ # On branch master
+ # Changes to be committed:
+ # (use "git reset HEAD <file>..." to unstage)
+ #
+ # new file: README
+ # modified: benchmarks.rb
+ ~
+ ~
+ ~
+ ".git/COMMIT_EDITMSG" 10L, 283C
+
+You can see that the default commit message contains the latest output of the `git status` command commented out and one empty line on top. You can remove these comments and type your commit message, or you can leave them there to help you remember what you’re committing. (For an even more explicit reminder of what you’ve modified, you can pass the `-v` option to `git commit`. Doing so also puts the diff of your change in the editor so you can see exactly what you did.) When you exit the editor, Git creates your commit with that commit message (with the comments and diff stripped out).
+
+Alternatively, you can type your commit message inline with the `commit` command by specifying it after a -m flag, like this:
+
+ $ git commit -m "Story 182: Fix benchmarks for speed"
+ [master]: created 463dc4f: "Fix benchmarks for speed"
+ 2 files changed, 3 insertions(+), 0 deletions(-)
+ create mode 100644 README
+
+Now you’ve created your first commit! You can see that the commit has given you some output about itself: which branch you committed to (master), what SHA-1 checksum the commit has (`463dc4f`), how many files were changed, and statistics about lines added and removed in the commit.
+
+Remember that the commit records the snapshot you set up in your staging area. Anything you didn’t stage is still sitting there modified; you can do another commit to add it to your history. Every time you perform a commit, you’re recording a snapshot of your project that you can revert to or compare to later.
+
+### Skipping the Staging Area ###
+
+Although it can be amazingly useful for crafting commits exactly how you want them, the staging area is sometimes a bit more complex than you need in your workflow. If you want to skip the staging area, Git provides a simple shortcut. Providing the `-a` option to the `git commit` command makes Git automatically stage every file that is already tracked before doing the commit, letting you skip the `git add` part:
+
+ $ git status
+ # On branch master
+ #
+ # Changed but not updated:
+ #
+ # modified: benchmarks.rb
+ #
+ $ git commit -a -m 'added new benchmarks'
+ [master 83e38c7] added new benchmarks
+ 1 files changed, 5 insertions(+), 0 deletions(-)
+
+Notice how you don’t have to run `git add` on the benchmarks.rb file in this case before you commit.
+
+### Removing Files ###
+
+To remove a file from Git, you have to remove it from your tracked files (more accurately, remove it from your staging area) and then commit. The `git rm` command does that and also removes the file from your working directory so you don’t see it as an untracked file next time around.
+
+If you simply remove the file from your working directory, it shows up under the “Changed but not updated” (that is, _unstaged_) area of your `git status` output:
+
+ $ rm grit.gemspec
+ $ git status
+ # On branch master
+ #
+ # Changed but not updated:
+ # (use "git add/rm <file>..." to update what will be committed)
+ #
+ # deleted: grit.gemspec
+ #
+
+Then, if you run `git rm`, it stages the file’s removal:
+
+ $ git rm grit.gemspec
+ rm 'grit.gemspec'
+ $ git status
+ # On branch master
+ #
+ # Changes to be committed:
+ # (use "git reset HEAD <file>..." to unstage)
+ #
+ # deleted: grit.gemspec
+ #
+
+The next time you commit, the file will be gone and no longer tracked. If you modified the file and added it to the index already, you must force the removal with the `-f` option. This is a safety feature to prevent accidental removal of data that hasn’t yet been recorded in a snapshot and that can’t be recovered from Git.
+
+Another useful thing you may want to do is to keep the file in your working tree but remove it from your staging area. In other words, you may want to keep the file on your hard drive but not have Git track it anymore. This is particularly useful if you forgot to add something to your `.gitignore` file and accidentally added it, like a large log file or a bunch of `.a` compiled files. To do this, use the `--cached` option:
+
+ $ git rm --cached readme.txt
+
+You can pass files, directories, and file-glob patterns to the `git rm` command. That means you can do things such as
+
+ $ git rm log/\*.log
+
+Note the backslash (`\`) in front of the `*`. This is necessary because Git does its own filename expansion in addition to your shell’s filename expansion. This command removes all files that have the `.log` extension in the `log/` directory. Or, you can do something like this:
+
+ $ git rm \*~
+
+This command removes all files that end with `~`.
+
+### Moving Files ###
+
+Unlike many other VCS systems, Git doesn’t explicitly track file movement. If you rename a file in Git, no metadata is stored in Git that tells it you renamed the file. However, Git is pretty smart about figuring that out after the fact — we’ll deal with detecting file movement a bit later.
+
+Thus it’s a bit confusing that Git has a `mv` command. If you want to rename a file in Git, you can run something like
+
+ $ git mv file_from file_to
+
+and it works fine. In fact, if you run something like this and look at the status, you’ll see that Git considers it a renamed file:
+
+ $ git mv README.txt README
+ $ git status
+ # On branch master
+ # Your branch is ahead of 'origin/master' by 1 commit.
+ #
+ # Changes to be committed:
+ # (use "git reset HEAD <file>..." to unstage)
+ #
+ # renamed: README.txt -> README
+ #
+
+However, this is equivalent to running something like this:
+
+ $ mv README.txt README
+ $ git rm README.txt
+ $ git add README
+
+Git figures out that it’s a rename implicitly, so it doesn’t matter if you rename a file that way or with the `mv` command. The only real difference is that `mv` is one command instead of three — it’s a convenience function. More important, you can use any tool you like to rename a file, and address the add/rm later, before you commit.
+
+## Viewing the Commit History ##
+
+After you have created several commits, or if you have cloned a repository with an existing commit history, you’ll probably want to look back to see what has happened. The most basic and powerful tool to do this is the `git log` command.
+
+These examples use a very simple project called simplegit that I often use for demonstrations. To get the project, run
+
+ git clone git://github.com/schacon/simplegit-progit.git
+
+When you run `git log` in this project, you should get output that looks something like this:
+
+ $ git log
+ commit ca82a6dff817ec66f44342007202690a93763949
+ Author: Scott Chacon <schacon@gee-mail.com>
+ Date: Mon Mar 17 21:52:11 2008 -0700
+
+ changed the version number
+
+ commit 085bb3bcb608e1e8451d4b2432f8ecbe6306e7e7
+ Author: Scott Chacon <schacon@gee-mail.com>
+ Date: Sat Mar 15 16:40:33 2008 -0700
+
+ removed unnecessary test code
+
+ commit a11bef06a3f659402fe7563abf99ad00de2209e6
+ Author: Scott Chacon <schacon@gee-mail.com>
+ Date: Sat Mar 15 10:31:28 2008 -0700
+
+ first commit
+
+By default, with no arguments, `git log` lists the commits made in that repository in reverse chronological order. That is, the most recent commits show up first. As you can see, this command lists each commit with its SHA-1 checksum, the author’s name and e-mail, the date written, and the commit message.
+
+A huge number and variety of options to the `git log` command are available to show you exactly what you’re looking for. Here, we’ll show you some of the most-used options.
+
+One of the more helpful options is `-p`, which shows the diff introduced in each commit. You can also use `-2`, which limits the output to only the last two entries:
+
+ $ git log –p -2
+ commit ca82a6dff817ec66f44342007202690a93763949
+ Author: Scott Chacon <schacon@gee-mail.com>
+ Date: Mon Mar 17 21:52:11 2008 -0700
+
+ changed the version number
+
+ diff --git a/Rakefile b/Rakefile
+ index a874b73..8f94139 100644
+ --- a/Rakefile
+ +++ b/Rakefile
+ @@ -5,7 +5,7 @@ require 'rake/gempackagetask'
+ spec = Gem::Specification.new do |s|
+ - s.version = "0.1.0"
+ + s.version = "0.1.1"
+ s.author = "Scott Chacon"
+
+ commit 085bb3bcb608e1e8451d4b2432f8ecbe6306e7e7
+ Author: Scott Chacon <schacon@gee-mail.com>
+ Date: Sat Mar 15 16:40:33 2008 -0700
+
+ removed unnecessary test code
+
+ diff --git a/lib/simplegit.rb b/lib/simplegit.rb
+ index a0a60ae..47c6340 100644
+ --- a/lib/simplegit.rb
+ +++ b/lib/simplegit.rb
+ @@ -18,8 +18,3 @@ class SimpleGit
+ end
+
+ end
+ -
+ -if $0 == __FILE__
+ - git = SimpleGit.new
+ - puts git.show
+ -end
+ \ No newline at end of file
+
+This option displays the same information but with a diff directly following each entry. This is very helpful for code review or to quickly browse what happened during a series of commits that a collaborator has added.
+You can also use a series of summarizing options with `git log`. For example, if you want to see some abbreviated stats for each commit, you can use the `--stat` option:
+
+ $ git log --stat
+ commit ca82a6dff817ec66f44342007202690a93763949
+ Author: Scott Chacon <schacon@gee-mail.com>
+ Date: Mon Mar 17 21:52:11 2008 -0700
+
+ changed the version number
+
+ Rakefile | 2 +-
+ 1 files changed, 1 insertions(+), 1 deletions(-)
+
+ commit 085bb3bcb608e1e8451d4b2432f8ecbe6306e7e7
+ Author: Scott Chacon <schacon@gee-mail.com>
+ Date: Sat Mar 15 16:40:33 2008 -0700
+
+ removed unnecessary test code
+
+ lib/simplegit.rb | 5 -----
+ 1 files changed, 0 insertions(+), 5 deletions(-)
+
+ commit a11bef06a3f659402fe7563abf99ad00de2209e6
+ Author: Scott Chacon <schacon@gee-mail.com>
+ Date: Sat Mar 15 10:31:28 2008 -0700
+
+ first commit
+
+ README | 6 ++++++
+ Rakefile | 23 +++++++++++++++++++++++
+ lib/simplegit.rb | 25 +++++++++++++++++++++++++
+ 3 files changed, 54 insertions(+), 0 deletions(-)
+
+As you can see, the `--stat` option prints below each commit entry a list of modified files, how many files were changed, and how many lines in those files were added and removed. It also puts a summary of the information at the end.
+Another really useful option is `--pretty`. This option changes the log output to formats other than the default. A few prebuilt options are available for you to use. The oneline option prints each commit on a single line, which is useful if you’re looking at a lot of commits. In addition, the `short`, `full`, and `fuller` options show the output in roughly the same format but with less or more information, respectively:
+
+ $ git log --pretty=oneline
+ ca82a6dff817ec66f44342007202690a93763949 changed the version number
+ 085bb3bcb608e1e8451d4b2432f8ecbe6306e7e7 removed unnecessary test code
+ a11bef06a3f659402fe7563abf99ad00de2209e6 first commit
+
+The most interesting option is `format`, which allows you to specify your own log output format. This is especially useful when you’re generating output for machine parsing — because you specify the format explicitly, you know it won’t change with updates to Git:
+
+ $ git log --pretty=format:"%h - %an, %ar : %s"
+ ca82a6d - Scott Chacon, 11 months ago : changed the version number
+ 085bb3b - Scott Chacon, 11 months ago : removed unnecessary test code
+ a11bef0 - Scott Chacon, 11 months ago : first commit
+
+Table 2-1 lists some of the more useful options that format takes.
+
+ Option Description of Output
+ %H Commit hash
+ %h Abbreviated commit hash
+ %T Tree hash
+ %t Abbreviated tree hash
+ %P Parent hashes
+ %p Abbreviated parent hashes
+ %an Author name
+ %ae Author e-mail
+ %ad Author date (format respects the –date= option)
+ %ar Author date, relative
+ %cn Committer name
+ %ce Committer email
+ %cd Committer date
+ %cr Committer date, relative
+ %s Subject
+
+You may be wondering what the difference is between _author_ and _committer_. The author is the person who originally wrote the work, whereas the committer is the person who last applied the work. So, if you send in a patch to a project and one of the core members applies the patch, both of you get credit — you as the author and the core member as the committer. We’ll cover this distinction a bit more in Chapter 5.
+
+The oneline and format options are particularly useful with another `log` option called `--graph`. This option adds a nice little ASCII graph showing your branch and merge history, which we can see our copy of the Grit project repository:
+
+ $ git log --pretty=format:"%h %s" --graph
+ * 2d3acf9 ignore errors from SIGCHLD on trap
+ * 5e3ee11 Merge branch 'master' of git://github.com/dustin/grit
+ |\
+ | * 420eac9 Added a method for getting the current branch.
+ * | 30e367c timeout code and tests
+ * | 5a09431 add timeout protection to grit
+ * | e1193f8 support for heads with slashes in them
+ |/
+ * d6016bc require time for xmlschema
+ * 11d191e Merge branch 'defunkt' into local
+
+Those are only some simple output-formatting options to `git log` — there are many more. Table 2-2 lists the options we’ve covered so far and some other common formatting options that may be useful, along with how they change the output of the log command.
+
+ Option Description
+ -p Show the patch introduced with each commit.
+ --stat Show statistics for files modified in each commit.
+ --shortstat Display only the changed/insertions/deletions line from the --stat command.
+ --name-only Show the list of files modified after the commit information.
+ --name-status Show the list of files affected with added/modified/deleted information as well.
+ --abbrev-commit Show only the first few characters of the SHA-1 checksum instead of all 40.
+ --relative-date Display the date in a relative format (for example, “2 weeks ago”) instead of using the full date format.
+ --graph Display an ASCII graph of the branch and merge history beside the log output.
+ --pretty Show commits in an alternate format. Options include oneline, short, full, fuller, and format (where you specify your own format).
+
+### Limiting Log Output ###
+
+In addition to output-formatting options, git log takes a number of useful limiting options — that is, options that let you show only a subset of commits. You’ve seen one such option already — the `-2` option, which show only the last two commits. In fact, you can do `-<n>`, where `n` is any integer to show the last `n` commits. In reality, you’re unlikely to use that often, because Git by default pipes all output through a pager so you see only one page of log output at a time.
+
+However, the time-limiting options such as `--since` and `--until` are very useful. For example, this command gets the list of commits made in the last two weeks:
+
+ $ git log --since=2.weeks
+
+This command works with lots of formats — you can specify a specific date (“2008-01-15”) or a relative date such as “2 years 1 day 3 minutes ago”.
+
+You can also filter the list to commits that match some search criteria. The `--author` option allows you to filter on a specific author, and the `--grep` option lets you search for keywords in the commit messages. (Note that if you want to specify both author and grep options, you have to add `--all-match` or the command will match commits with either.)
+
+The last really useful option to pass to `git log` as a filter is a path. If you specify a directory or file name, you can limit the log output to commits that introduced a change to those files. This is always the last option and is generally preceded by double dashes (`--`) to separate the paths from the options.
+
+In Table 2-3 we’ll list these and a few other common options for your reference.
+
+ Option Description
+ -(n) Show only the last n commits
+ --since, --after Limit the commits to those made after the specified date.
+ --until, --before Limit the commits to those made before the specified date.
+ --author Only show commits in which the author entry matches the specified string.
+ --committer Only show commits in which the committer entry matches the specified string.
+
+For example, if you want to see which commits modifying test files in the Git source code history were committed by Junio Hamano and were not merges in the month of October 2008, you can run something like this:
+
+ $ git log --pretty="%h - %s" --author=gitster --since="2008-10-01" \
+ --before="2008-11-01" --no-merges -- t/
+ 5610e3b - Fix testcase failure when extended attribute
+ acd3b9e - Enhance hold_lock_file_for_{update,append}()
+ f563754 - demonstrate breakage of detached checkout wi
+ d1a43f2 - reset --hard/read-tree --reset -u: remove un
+ 51a94af - Fix "checkout --track -b newbranch" on detac
+ b0ad11e - pull: allow "git pull origin $something:$cur
+
+Of the nearly 20,000 commits in the Git source code history, this command shows the 6 that match those criteria.
+
+### Using a GUI to Visualize History ###
+
+If you like to use a more graphical tool to visualize your commit history, you may want to take a look at a Tcl/Tk program called gitk that is distributed with Git. Gitk is basically a visual `git log` tool, and it accepts nearly all the filtering options that `git log` does. If you type gitk on the command line in your project, you should see something like Figure 2-2.
+
+Insert 18333fig0202.png
+Figure 2-2. The gitk history visualizer.
+
+You can see the commit history in the top half of the window along with a nice ancestry graph. The diff viewer in the bottom half of the window shows you the changes introduced at any commit you click.
+
+## Undoing Things ##
+
+At any stage, you may want to undo something. Here, we’ll review a few basic tools for undoing changes that you’ve made. Be careful, because you can’t always undo some of these undos. This is one of the few areas in Git where you may lose some work if you do it wrong.
+
+### Changing Your Last Commit ###
+
+One of the common undos takes place when you commit too early and possibly forget to add some files, or you mess up your commit message. If you want to try that commit again, you can run commit with the `--amend` option:
+
+ $ git commit --amend
+
+This command takes your staging area and uses it for the commit. If you’ve have made no changes since your last commit (for instance, you run this command immediately after your previous commit), then your snapshot will look exactly the same and all you’ll change is your commit message.
+
+The same commit-message editor fires up, but it already contains the message of your previous commit. You can edit the message the same as always, but it overwrites your previous commit.
+
+As an example, if you commit and then realize you forgot to stage the changes in a file you wanted to add to this commit, you can do something like this:
+
+ $ git commit -m 'initial commit'
+ $ git add forgotten_file
+ $ git commit --amend
+
+All three of these commands end up with a single commit — the second commit replaces the results of the first.
+
+### Unstaging a Staged File ###
+
+The next two sections demonstrate how to wrangle your staging area and working directory changes. The nice part is that the command you use to determine the state of those two areas also reminds you how to undo changes to them. For example, let’s say you’ve changed two files and want to commit them as two separate changes, but you accidentally type `git add *` and stage them both. How can you unstage one of the two? The `git status` command reminds you:
+
+ $ git add .
+ $ git status
+ # On branch master
+ # Changes to be committed:
+ # (use "git reset HEAD <file>..." to unstage)
+ #
+ # modified: README.txt
+ # modified: benchmarks.rb
+ #
+
+Right below the “Changes to be committed” text, it says use `git reset HEAD <file>...` to unstage. So, let’s use that advice to unstage the benchmarks.rb file:
+
+ $ git reset HEAD benchmarks.rb
+ benchmarks.rb: locally modified
+ $ git status
+ # On branch master
+ # Changes to be committed:
+ # (use "git reset HEAD <file>..." to unstage)
+ #
+ # modified: README.txt
+ #
+ # Changed but not updated:
+ # (use "git add <file>..." to update what will be committed)
+ # (use "git checkout -- <file>..." to discard changes in working directory)
+ #
+ # modified: benchmarks.rb
+ #
+
+The command is a bit strange, but it works. The benchmarks.rb file is modified but once again unstaged.
+
+### Unmodifying a Modified File ###
+
+What if you realize that you don’t want to keep your changes to the benchmarks.rb file? How can you easily unmodify it — revert it back to what it looked like when you last committed (or initially cloned, or however you got it into your working directory)? Luckily, `git status` tells you how to do that, too. In the last example output, the unstaged area looks like this:
+
+ # Changed but not updated:
+ # (use "git add <file>..." to update what will be committed)
+ # (use "git checkout -- <file>..." to discard changes in working directory)
+ #
+ # modified: benchmarks.rb
+ #
+
+It tells you pretty explicitly how to discard the changes you’ve made (at least, the newer versions of Git, 1.6.1 and later, do this — if you have an older version, we highly recommend upgrading it to get some of these nicer usability features). Let’s do what it says:
+
+ $ git checkout -- benchmarks.rb
+ $ git status
+ # On branch master
+ # Changes to be committed:
+ # (use "git reset HEAD <file>..." to unstage)
+ #
+ # modified: README.txt
+ #
+
+You can see that the changes have been reverted. You should also realize that this is a dangerous command: any changes you made to that file are gone — you just copied another file over it. Don’t ever use this command unless you absolutely know that you don’t want the file. If you just need to get it out of the way, we’ll go over stashing and branching in the next chapter; these are generally better ways to go.
+
+Remember, anything that is committed in Git can almost always be recovered. Even commits that were on branches that were deleted or commits that were overwritten with an `--amend` commit can be recovered (see Chapter 9 for data recovery). However, anything you lose that was never committed is likely never to be seen again.
+
+## Working with Remotes ##
+
+To be able to collaborate on any Git project, you need to know how to manage your remote repositories. Remote repositories are versions of your project that are hosted on the Internet or network somewhere. You can have several of them, each of which generally is either read-only or read/write for you. Collaborating with others involves managing these remote repositories and pushing and pulling data to and from them when you need to share work.
+Managing remote repositories includes knowing how to add remote repositories, remove remotes that are no longer valid, manage various remote branches and define them as being tracked or not, and more. In this section, we’ll cover these remote-management skills.
+
+### Showing Your Remotes ###
+
+To see which remote servers you have configured, you can run the git remote command. It lists the shortnames of each remote handle you’ve specified. If you’ve cloned your repository, you should at least see origin — that is the default name Git gives to the server you cloned from:
+
+ $ git clone git://github.com/schacon/ticgit.git
+ Initialized empty Git repository in /private/tmp/ticgit/.git/
+ remote: Counting objects: 595, done.
+ remote: Compressing objects: 100% (269/269), done.
+ remote: Total 595 (delta 255), reused 589 (delta 253)
+ Receiving objects: 100% (595/595), 73.31 KiB | 1 KiB/s, done.
+ Resolving deltas: 100% (255/255), done.
+ $ cd ticgit
+ $ git remote
+ origin
+
+You can also specify `-v`, which shows you the URL that Git has stored for the shortname to be expanded to:
+
+ $ git remote -v
+ origin git://github.com/schacon/ticgit.git
+
+If you have more than one remote, the command lists them all. For example, my Grit repository looks something like this.
+
+ $ cd grit
+ $ git remote -v
+ bakkdoor git://github.com/bakkdoor/grit.git
+ cho45 git://github.com/cho45/grit.git
+ defunkt git://github.com/defunkt/grit.git
+ koke git://github.com/koke/grit.git
+ origin git@github.com:mojombo/grit.git
+
+This means we can pull contributions from any of these users pretty easily. But notice that only the origin remote is an SSH URL, so it’s the only one I can push to (we’ll cover why this is in Chapter 4).
+
+### Adding Remote Repositories ###
+
+I’ve mentioned and given some demonstrations of adding remote repositories in previous sections, but here is how to do it explicitly. To add a new remote Git repository as a shortname you can reference easily, run `git remote add [shortname] [url]`:
+
+ $ git remote
+ origin
+ $ git remote add pb git://github.com/paulboone/ticgit.git
+ $ git remote -v
+ origin git://github.com/schacon/ticgit.git
+ pb git://github.com/paulboone/ticgit.git
+
+Now you can use the string pb on the command line in lieu of the whole URL. For example, if you want to fetch all the information that Paul has but that you don’t yet have in your repository, you can run git fetch pb:
+
+ $ git fetch pb
+ remote: Counting objects: 58, done.
+ remote: Compressing objects: 100% (41/41), done.
+ remote: Total 44 (delta 24), reused 1 (delta 0)
+ Unpacking objects: 100% (44/44), done.
+ From git://github.com/paulboone/ticgit
+ * [new branch] master -> pb/master
+ * [new branch] ticgit -> pb/ticgit
+
+Paul’s master branch is accessible locally as `pb/master` — you can merge it into one of your branches, or you can check out a local branch at that point if you want to inspect it.
+
+### Fetching and Pulling from Your Remotes ###
+
+As you just saw, to get data from your remote projects, you can run:
+
+ $ git fetch [remote-name]
+
+The command goes out to that remote project and pulls down all the data from that remote project that you don’t have yet. After you do this, you should have references to all the branches from that remote, which you can merge in or inspect at any time. (We’ll go over what branches are and how to use them in much more detail in Chapter 3.)
+
+If you clone a repository, the command automatically adds that remote repository under the name origin. So, `git fetch origin` fetches any new work that has been pushed to that server since you cloned (or last fetched from) it. It’s important to note that the fetch command pulls the data to your local repository — it doesn’t automatically merge it with any of your work or modify what you’re currently working on. You have to merge it manually into your work when you’re ready.
+
+If you have a branch set up to track a remote branch (see the next section and Chapter 3 for more information), you can use the `git pull` command to automatically fetch and then merge a remote branch into your current branch. This may be an easier or more comfortable workflow for you; and by default, the `git clone` command automatically sets up your local master branch to track the remote master branch on the server you cloned from (assuming the remote has a master branch). Running `git pull` generally fetches data from the server you originally cloned from and automatically tries to merge it into the code you’re currently working on.
+
+### Pushing to Your Remotes ###
+
+When you have your project at a point that you want to share, you have to push it upstream. The command for this is simple: `git push [remote-name] [branch-name]`. If you want to push your master branch to your `origin` server (again, cloning generally sets up both of those names for you automatically), then you can run this to push your work back up to the server:
+
+ $ git push origin master
+
+This command works only if you cloned from a server to which you have write access and if nobody has pushed in the meantime. If you and someone else clone at the same time and they push upstream and then you push upstream, your push will rightly be rejected. You’ll have to pull down their work first and incorporate it into yours before you’ll be allowed to push. See Chapter 3 for more detailed information on how to push to remote servers.
+
+### Inspecting a Remote ###
+
+If you want to see more information about a particular remote, you can use the `git remote show [remote-name]` command. If you run this command with a particular shortname, such as `origin`, you get something like this:
+
+ $ git remote show origin
+ * remote origin
+ URL: git://github.com/schacon/ticgit.git
+ Remote branch merged with 'git pull' while on branch master
+ master
+ Tracked remote branches
+ master
+ ticgit
+
+It lists the URL for the remote repository as well as the tracking branch information. The command helpfully tells you that if you’re on the master branch and you run `git pull`, it will automatically merge in the master branch on the remote after it fetches all the remote references. It also lists all the remote references it has pulled down.
+
+That is a simple example you’re likely to encounter. When you’re using Git more heavily, however, you may see much more information from `git remote show`:
+
+ $ git remote show origin
+ * remote origin
+ URL: git@github.com:defunkt/github.git
+ Remote branch merged with 'git pull' while on branch issues
+ issues
+ Remote branch merged with 'git pull' while on branch master
+ master
+ New remote branches (next fetch will store in remotes/origin)
+ caching
+ Stale tracking branches (use 'git remote prune')
+ libwalker
+ walker2
+ Tracked remote branches
+ acl
+ apiv2
+ dashboard2
+ issues
+ master
+ postgres
+ Local branch pushed with 'git push'
+ master:master
+
+This command shows which branch is automatically pushed when you run `git push` on certain branches. It also shows you which remote branches on the server you don’t yet have, which remote branches you have that have been removed from the server, and multiple branches that are automatically merged when you run `git pull`.
+
+### Removing and Renaming Remotes ###
+
+If you want to rename a reference, in newer versions of Git you can run `git remote rename` to change a remote’s shortname. For instance, if you want to rename `pb` to `paul`, you can do so with `git remote rename`:
+
+ $ git remote rename pb paul
+ $ git remote
+ origin
+ paul
+
+It’s worth mentioning that this changes your remote branch names, too. What used to be referenced at `pb/master` is now at `paul/master`.
+
+If you want to remove a reference for some reason — you’ve moved the server or are no longer using a particular mirror, or perhaps a contributor isn’t contributing anymore — you can use `git remote rm`:
+
+ $ git remote rm paul
+ $ git remote
+ origin
+
+## Tagging ##
+
+Like most VCSs, Git has the ability to tag specific points in history as being important. Generally, people use this functionality to mark release points (v1.0, and so on). In this section, you’ll learn how to list the available tags, how to create new tags, and what the different types of tags are.
+
+### Listing Your Tags ###
+
+Listing the available tags in Git is straightforward. Just type `git tag`:
+
+ $ git tag
+ v0.1
+ v1.3
+
+This command lists the tags in alphabetical order; the order in which they appear has no real importance.
+
+You can also search for tags with a particular pattern. The Git source repo, for instance, contains more than 240 tags. If you’re only interested in looking at the 1.4.2 series, you can run this:
+
+ $ git tag -l 'v1.4.2.*'
+ v1.4.2.1
+ v1.4.2.2
+ v1.4.2.3
+ v1.4.2.4
+
+### Creating Tags ###
+
+Git uses two main types of tags: lightweight and annotated. A lightweight tag is very much like a branch that doesn’t change — it’s just a pointer to a specific commit. Annotated tags, however, are stored as full objects in the Git database. They’re checksummed; contain the tagger name, e-mail, and date; have a tagging message; and can be signed and verified with GNU Privacy Guard (GPG). It’s generally recommended that you create annotated tags so you can have all this information; but if you want a temporary tag or for some reason don’t want to keep the other information, lightweight tags are available too.
+
+### Annotated Tags ###
+
+Creating an annotated tag in Git is simple. The easiest way is to specify `-a` when you run the `tag` command:
+
+ $ git tag -a v1.4 -m 'my version 1.4'
+ $ git tag
+ v0.1
+ v1.3
+ v1.4
+
+The `-m` specifies a tagging message, which is stored with the tag. If you don’t specify a message for an annotated tag, Git launches your editor so you can type it in.
+
+You can see the tag data along with the commit that was tagged by using the `git show` command:
+
+ $ git show v1.4
+ tag v1.4
+ Tagger: Scott Chacon <schacon@gee-mail.com>
+ Date: Mon Feb 9 14:45:11 2009 -0800
+
+ my version 1.4
+ commit 15027957951b64cf874c3557a0f3547bd83b3ff6
+ Merge: 4a447f7... a6b4c97...
+ Author: Scott Chacon <schacon@gee-mail.com>
+ Date: Sun Feb 8 19:02:46 2009 -0800
+
+ Merge branch 'experiment'
+
+That shows the tagger information, the date the commit was tagged, and the annotation message before showing the commit information.
+
+### Signed Tags ###
+
+You can also sign your tags with GPG, assuming you have a private key. All you have to do is use `-s` instead of `-a`:
+
+ $ git tag -s v1.5 -m 'my signed 1.5 tag'
+ You need a passphrase to unlock the secret key for
+ user: "Scott Chacon <schacon@gee-mail.com>"
+ 1024-bit DSA key, ID F721C45A, created 2009-02-09
+
+If you run `git show` on that tag, you can see your GPG signature attached to it:
+
+ $ git show v1.5
+ tag v1.5
+ Tagger: Scott Chacon <schacon@gee-mail.com>
+ Date: Mon Feb 9 15:22:20 2009 -0800
+
+ my signed 1.5 tag
+ -----BEGIN PGP SIGNATURE-----
+ Version: GnuPG v1.4.8 (Darwin)
+
+ iEYEABECAAYFAkmQurIACgkQON3DxfchxFr5cACeIMN+ZxLKggJQf0QYiQBwgySN
+ Ki0An2JeAVUCAiJ7Ox6ZEtK+NvZAj82/
+ =WryJ
+ -----END PGP SIGNATURE-----
+ commit 15027957951b64cf874c3557a0f3547bd83b3ff6
+ Merge: 4a447f7... a6b4c97...
+ Author: Scott Chacon <schacon@gee-mail.com>
+ Date: Sun Feb 8 19:02:46 2009 -0800
+
+ Merge branch 'experiment'
+
+A bit later, you’ll learn how to verify signed tags.
+
+### Lightweight Tags ###
+
+Another way to tag commits is with a lightweight tag. This is basically the commit checksum stored in a file — no other information is kept. To create a lightweight tag, don’t supply the `-a`, `-s`, or `-m` option:
+
+ $ git tag v1.4-lw
+ $ git tag
+ v0.1
+ v1.3
+ v1.4
+ v1.4-lw
+ v1.5
+
+This time, if you run `git show` on the tag, you don’t see the extra tag information. The command just shows the commit:
+
+ $ git show v1.4-lw
+ commit 15027957951b64cf874c3557a0f3547bd83b3ff6
+ Merge: 4a447f7... a6b4c97...
+ Author: Scott Chacon <schacon@gee-mail.com>
+ Date: Sun Feb 8 19:02:46 2009 -0800
+
+ Merge branch 'experiment'
+
+### Verifying Tags ###
+
+To verify a signed tag, you use `git tag -v [tag-name]`. This command uses GPG to verify the signature. You need the signer’s public key in your keyring for this to work properly:
+
+ $ git tag -v v1.4.2.1
+ object 883653babd8ee7ea23e6a5c392bb739348b1eb61
+ type commit
+ tag v1.4.2.1
+ tagger Junio C Hamano <junkio@cox.net> 1158138501 -0700
+
+ GIT 1.4.2.1
+
+ Minor fixes since 1.4.2, including git-mv and git-http with alternates.
+ gpg: Signature made Wed Sep 13 02:08:25 2006 PDT using DSA key ID F3119B9A
+ gpg: Good signature from "Junio C Hamano <junkio@cox.net>"
+ gpg: aka "[jpeg image of size 1513]"
+ Primary key fingerprint: 3565 2A26 2040 E066 C9A7 4A7D C0C6 D9A4 F311 9B9A
+
+If you don’t have the signer’s public key, you get something like this instead:
+
+ gpg: Signature made Wed Sep 13 02:08:25 2006 PDT using DSA key ID F3119B9A
+ gpg: Can't check signature: public key not found
+ error: could not verify the tag 'v1.4.2.1'
+
+### Tagging Later ###
+
+You can also tag commits after you’ve moved past them. Suppose your commit history looks like this:
+
+ $ git log --pretty=oneline
+ 15027957951b64cf874c3557a0f3547bd83b3ff6 Merge branch 'experiment'
+ a6b4c97498bd301d84096da251c98a07c7723e65 beginning write support
+ 0d52aaab4479697da7686c15f77a3d64d9165190 one more thing
+ 6d52a271eda8725415634dd79daabbc4d9b6008e Merge branch 'experiment'
+ 0b7434d86859cc7b8c3d5e1dddfed66ff742fcbc added a commit function
+ 4682c3261057305bdd616e23b64b0857d832627b added a todo file
+ 166ae0c4d3f420721acbb115cc33848dfcc2121a started write support
+ 9fceb02d0ae598e95dc970b74767f19372d61af8 updated rakefile
+ 964f16d36dfccde844893cac5b347e7b3d44abbc commit the todo
+ 8a5cbc430f1a9c3d00faaeffd07798508422908a updated readme
+
+Now, suppose you forgot to tag the project at v1.2, which was at the "updated rakefile" commit. You can add it after the fact. To tag that commit, you specify the commit checksum (or part of it) at the end of the command:
+
+ $ git tag -a v1.2 9fceb02
+
+You can see that you’ve tagged the commit:
+
+ $ git tag
+ v0.1
+ v1.2
+ v1.3
+ v1.4
+ v1.4-lw
+ v1.5
+
+ $ git show v1.2
+ tag v1.2
+ Tagger: Scott Chacon <schacon@gee-mail.com>
+ Date: Mon Feb 9 15:32:16 2009 -0800
+
+ version 1.2
+ commit 9fceb02d0ae598e95dc970b74767f19372d61af8
+ Author: Magnus Chacon <mchacon@gee-mail.com>
+ Date: Sun Apr 27 20:43:35 2008 -0700
+
+ updated rakefile
+ ...
+
+### Sharing Tags ###
+
+By default, the `git push` command doesn’t transfer tags to remote servers. You will have to explicitly push tags to a shared server after you have created them. This process is just like sharing remote branches – you can run `git push origin [tagname]`.
+
+ $ git push origin v1.5
+ Counting objects: 50, done.
+ Compressing objects: 100% (38/38), done.
+ Writing objects: 100% (44/44), 4.56 KiB, done.
+ Total 44 (delta 18), reused 8 (delta 1)
+ To git@github.com:schacon/simplegit.git
+ * [new tag] v1.5 -> v1.5
+
+If you have a lot of tags that you want to push up at once, you can also use the `--tags` option to the `git push` command. This will transfer all of your tags to the remote server that are not already there.
+
+ $ git push origin --tags
+ Counting objects: 50, done.
+ Compressing objects: 100% (38/38), done.
+ Writing objects: 100% (44/44), 4.56 KiB, done.
+ Total 44 (delta 18), reused 8 (delta 1)
+ To git@github.com:schacon/simplegit.git
+ * [new tag] v0.1 -> v0.1
+ * [new tag] v1.2 -> v1.2
+ * [new tag] v1.4 -> v1.4
+ * [new tag] v1.4-lw -> v1.4-lw
+ * [new tag] v1.5 -> v1.5
+
+Now, when someone else clones or pulls from your repository, they will get all your tags as well.
+
+## Tips and Tricks ##
+
+Before we finish this chapter on basic Git, a few little tips and tricks may make your Git experience a bit simpler, easier, or more familiar. Many people use Git without using any of these tips, and we won’t refer to them or assume you’ve used them later in the book; but you should probably know how to do them.
+
+### Auto-Completion ###
+
+If you use the Bash shell, Git comes with a nice auto-completion script you can enable. Download the Git source code, and look in the `contrib/completion` directory; there should be a file called `git-completion.bash`. Copy this file to your home directory, and add this to your `.bashrc` file:
+
+ source ~/.git-completion.bash
+
+If you want to set up Git to automatically have Bash shell completion for all users, copy this script to the `/opt/local/etc/bash_completion.d` directory on Mac systems or to the `/etc/bash_completion.d/` directory on Linux systems. This is a directory of scripts that Bash will automatically load to provide shell completions.
+
+If you’re using Windows with Git Bash, which is the default when installing Git on Windows with msysGit, auto-completion should be preconfigured.
+
+Press the Tab key when you’re writing a Git command, and it should return a set of suggestions for you to pick from:
+
+ $ git co<tab><tab>
+ commit config
+
+In this case, typing git co and then pressing the Tab key twice suggests commit and config. Adding `m<tab>` completes `git commit` automatically.
+
+This also works with options, which is probably more useful. For instance, if you’re running a `git log` command and can’t remember one of the options, you can start typing it and press Tab to see what matches:
+
+ $ git log --s<tab>
+ --shortstat --since= --src-prefix= --stat --summary
+
+That’s a pretty nice trick and may save you some time and documentation reading.
+
+### Git Aliases ###
+
+Git doesn’t infer your command if you type it in partially. If you don’t want to type the entire text of each of the Git commands, you can easily set up an alias for each command using `git config`. Here are a couple of examples you may want to set up:
+
+ $ git config --global alias.co checkout
+ $ git config --global alias.br branch
+ $ git config --global alias.ci commit
+ $ git config --global alias.st status
+
+This means that, for example, instead of typing `git commit`, you just need to type `git ci`. As you go on using Git, you’ll probably use other commands frequently as well; in this case, don’t hesitate to create new aliases.
+
+This technique can also be very useful in creating commands that you think should exist. For example, to correct the usability problem you encountered with unstaging a file, you can add your own unstage alias to Git:
+
+ $ git config --global alias.unstage 'reset HEAD --'
+
+This makes the following two commands equivalent:
+
+ $ git unstage fileA
+ $ git reset HEAD fileA
+
+This seems a bit clearer. It’s also common to add a `last` command, like this:
+
+ $ git config --global alias.last 'log -1 HEAD'
+
+This way, you can see the last commit easily:
+
+ $ git last
+ commit 66938dae3329c7aebe598c2246a8e6af90d04646
+ Author: Josh Goebel <dreamer3@example.com>
+ Date: Tue Aug 26 19:48:51 2008 +0800
+
+ test for current head
+
+ Signed-off-by: Scott Chacon <schacon@example.com>
+
+As you can tell, Git simply replaces the new command with whatever you alias it for. However, maybe you want to run an external command, rather than a Git subcommand. In that case, you start the command with a `!` character. This is useful if you write your own tools that work with a Git repository. We can demonstrate by aliasing `git visual` to run `gitk`:
+
+ $ git config --global alias.visual "!gitk"
+
+## Summary ##
+
+At this point, you can do all the basic local Git operations — creating or cloning a repository, making changes, staging and committing those changes, and viewing the history of all the changes the repository has been through. Next, we’ll cover Git’s killer feature: its branching model.
View
598 fr/03-git-branching/01-chapter3.markdown
@@ -0,0 +1,598 @@
+# Git Branching #
+
+Nearly every VCS has some form of branching support. Branching means you diverge from the main line of development and continue to do work without messing with that main line. In many VCS tools, this is a somewhat expensive process, often requiring you to create a new copy of your source code directory, which can take a long time for large projects.
+
+Some people refer to the branching model in Git as its “killer feature,” and it certainly sets Git apart in the VCS community. Why is it so special? The way Git branches is incredibly lightweight, making branching operations nearly instantaneous and switching back and forth between branches generally just as fast. Unlike many other VCSs, Git encourages a workflow that branches and merges often, even multiple times in a day. Understanding and mastering this feature gives you a powerful and unique tool and can literally change the way that you develop.
+
+## What a Branch Is ##
+
+To really understand the way Git does branching, we need to take a step back and examine how Git stores its data. As you may remember from Chapter 1, Git doesn’t store data as a series of changesets or deltas, but instead as a series of snapshots.
+
+When you commit in Git, Git stores a commit object that contains a pointer to the snapshot of the content you staged, the author and message metadata, and zero or more pointers to the commit or commits that were the direct parents of this commit: zero parents for the first commit, one parent for a normal commit, and multiple parents for a commit that results from a merge of two or more branches.
+
+To visualize this, let’s assume that you have a directory containing three files, and you stage them all and commit. Staging the files checksums each one (the SHA-1 hash we mentioned in Chapter 1), stores that version of the file in the Git repository (Git refers to them as blobs), and adds that checksum to the staging area:
+
+ $ git add README test.rb LICENSE
+ $ git commit -m 'initial commit of my project'
+
+When you create the commit by running `git commit`, Git checksums each subdirectory (in this case, just the root project directory) and stores those tree objects in the Git repository. Git then creates a commit object that has the metadata and a pointer to the root project tree so it can re-create that snapshot when needed.
+
+Your Git repository now contains five objects: one blob for the contents of each of your three files, one tree that lists the contents of the directory and specifies which file names are stored as which blobs, and one commit with the pointer to that root tree and all the commit metadata. Conceptually, the data in your Git repository looks something like Figure 3-1.
+
+Insert 18333fig0301.png
+Figure 3-1. Single commit repository data.
+
+If you make some changes and commit again, the next commit stores a pointer to the commit that came immediately before it. After two more commits, your history might look something like Figure 3-2.
+
+Insert 18333fig0302.png
+Figure 3-2. Git object data for multiple commits.
+
+A branch in Git is simply a lightweight movable pointer to one of these commits. The default branch name in Git is master. As you initially make commits, you’re given a master branch that points to the last commit you made. Every time you commit, it moves forward automatically.
+
+Insert 18333fig0303.png
+Figure 3-3. Branch pointing into the commit data’s history.
+
+What happens if you create a new branch? Well, doing so creates a new pointer for you to move around. Let’s say you create a new branch called testing. You do this with the `git branch` command:
+
+ $ git branch testing
+
+This creates a new pointer at the same commit you’re currently on (see Figure 3-4).
+
+Insert 18333fig0304.png
+Figure 3-4. Multiple branches pointing into the commit’s data history.
+
+How does Git know what branch you’re currently on? It keeps a special pointer called HEAD. Note that this is a lot different than the concept of HEAD in other VCSs you may be used to, such as Subversion or CVS. In Git, this is a pointer to the local branch you’re currently on. In this case, you’re still on master. The git branch command only created a new branch — it didn’t switch to that branch (see Figure 3-5).
+
+Insert 18333fig0305.png
+Figure 3-5. HEAD file pointing to the branch you’re on.
+
+To switch to an existing branch, you run the `git checkout` command. Let’s switch to the new testing branch:
+
+ $ git checkout testing
+
+This moves HEAD to point to the testing branch (see Figure 3-6).
+
+Insert 18333fig0306.png
+Figure 3-6. HEAD points to another branch when you switch branches.
+
+What is the significance of that? Well, let’s do another commit:
+
+ $ vim test.rb
+ $ git commit -a -m 'made a change'
+
+Figure 3-7 illustrates the result.
+
+Insert 18333fig0307.png
+Figure 3-7. The branch that HEAD points to moves forward with each commit.
+
+This is interesting, because now your testing branch has moved forward, but your master branch still points to the commit you were on when you ran `git checkout` to switch branches. Let’s switch back to the master branch:
+
+ $ git checkout master
+
+Figure 3-8 shows the result.
+
+Insert 18333fig0308.png
+Figure 3-8. HEAD moves to another branch on a checkout.
+
+That command did two things. It moved the HEAD pointer back to point to the master branch, and it reverted the files in your working directory back to the snapshot that master points to. This also means the changes you make from this point forward will diverge from an older version of the project. It essentially rewinds the work you’ve done in your testing branch temporarily so you can go in a different direction.
+
+Let’s make a few changes and commit again:
+
+ $ vim test.rb
+ $ git commit -a -m 'made other changes'
+
+Now your project history has diverged (see Figure 3-9). You created and switched to a branch, did some work on it, and then switched back to your main branch and did other work. Both of those changes are isolated in separate branches: you can switch back and forth between the branches and merge them together when you’re ready. And you did all that with simple `branch` and `checkout` commands.
+
+Insert 18333fig0309.png
+Figure 3-9. The branch histories have diverged.
+
+Because a branch in Git is in actuality a simple file that contains the 40 character SHA-1 checksum of the commit it points to, branches are cheap to create and destroy. Creating a new branch is as quick and simple as writing 41 bytes to a file (40 characters and a newline).
+
+This is in sharp contrast to the way most VCS tools branch, which involves copying all of the project’s files into a second directory. This can take several seconds or even minutes, depending on the size of the project, whereas in Git the process is always instantaneous. Also, because we’re recording the parents when we commit, finding a proper merge base for merging is automatically done for us and is generally very easy to do. These features help encourage developers to create and use branches often.
+
+Let’s see why you should do so.
+
+## Basic Branching and Merging ##
+
+Let’s go through a simple example of branching and merging with a workflow that you might use in the real world. You’ll follow these steps:
+
+1. Do work on a web site.
+2. Create a branch for a new story you’re working on.
+3. Do some work in that branch.
+
+At this stage, you’ll receive a call that another issue is critical and you need a hotfix. You’ll do the following:
+
+1. Revert back to your production branch.
+2. Create a branch to add the hotfix.
+3. After it’s tested, merge the hotfix branch, and push to production.
+4. Switch back to your original story and continue working.
+
+### Basic Branching ###
+
+First, let’s say you’re working on your project and have a couple of commits already (see Figure 3-10).
+
+Insert 18333fig0310.png
+Figure 3-10. A short and simple commit history.
+
+You’ve decided that you’re going to work on issue #53 in whatever issue-tracking system your company uses. To be clear, Git isn’t tied into any particular issue-tracking system; but because issue #53 is a focused topic that you want to work on, you’ll create a new branch in which to work. To create a branch and switch to it at the same time, you can run the `git checkout` command with the `-b` switch:
+
+ $ git checkout -b iss53
+ Switched to a new branch "iss53"
+
+This is shorthand for:
+
+ $ git branch iss53
+ $ git checkout iss53
+
+Figure 3-11 illustrates the result.
+
+Insert 18333fig0311.png
+Figure 3-11. Creating a new branch pointer.
+
+You work on your web site and do some commits. Doing so moves the `iss53` branch forward, because you have it checked out (that is, your HEAD is pointing to it; see Figure 3-12):
+
+ $ vim index.html
+ $ git commit -a -m 'added a new footer [issue 53]'
+
+Insert 18333fig0312.png
+Figure 3-12. The iss53 branch has moved forward with your work.
+
+Now you get the call that there is an issue with the web site, and you need to fix it immediately. With Git, you don’t have to deploy your fix along with the `iss53` changes you’ve made, and you don’t have to put a lot of effort into reverting those changes before you can work on applying your fix to what is in production. All you have to do is switch back to your master branch.
+
+However, before you do that, note that if your working directory or staging area has uncommitted changes that conflict with the branch you’re checking out, Git won’t let you switch branches. It’s best to have a clean working state when you switch branches. There are ways to get around this (namely, stashing and commit amending) that we’ll cover later. For now, you’ve committed all your changes, so you can switch back to your master branch:
+
+ $ git checkout master
+ Switched to branch "master"
+
+At this point, your project working directory is exactly the way it was before you started working on issue #53, and you can concentrate on your hotfix. This is an important point to remember: Git resets your working directory to look like the snapshot of the commit that the branch you check out points to. It adds, removes, and modifies files automatically to make sure your working copy is what the branch looked like on your last commit to it.
+
+Next, you have a hotfix to make. Let’s create a hotfix branch on which to work until it’s completed (see Figure 3-13):
+
+ $ git checkout -b 'hotfix'
+ Switched to a new branch "hotfix"
+ $ vim index.html
+ $ git commit -a -m 'fixed the broken email address'
+ [hotfix]: created 3a0874c: "fixed the broken email address"
+ 1 files changed, 0 insertions(+), 1 deletions(-)
+
+Insert 18333fig0313.png
+Figure 3-13. hotfix branch based back at your master branch point.
+
+You can run your tests, make sure the hotfix is what you want, and merge it back into your master branch to deploy to production. You do this with the `git merge` command:
+
+ $ git checkout master
+ $ git merge hotfix
+ Updating f42c576..3a0874c
+ Fast forward
+ README | 1 -
+ 1 files changed, 0 insertions(+), 1 deletions(-)
+
+You’ll notice the phrase "Fast forward" in that merge. Because the commit pointed to by the branch you merged in was directly upstream of the commit you’re on, Git moves the pointer forward. To phrase that another way, when you try to merge one commit with a commit that can be reached by following the first commit’s history, Git simplifies things by moving the pointer forward because there is no divergent work to merge together — this is called a "fast forward".
+
+Your change is now in the snapshot of the commit pointed to by the `master` branch, and you can deploy your change (see Figure 3-14).
+
+Insert 18333fig0314.png
+Figure 3-14. Your master branch points to the same place as your hotfix branch after the merge.
+
+After your super-important fix is deployed, you’re ready to switch back to the work you were doing before you were interrupted. However, first you’ll delete the `hotfix` branch, because you no longer need it — the `master` branch points at the same place. You can delete it with the `-d` option to `git branch`:
+
+ $ git branch -d hotfix
+ Deleted branch hotfix (3a0874c).
+
+Now you can switch back to your work-in-progress branch on issue #53 and continue working on it (see Figure 3-15):
+
+ $ git checkout iss53
+ Switched to branch "iss53"
+ $ vim index.html
+ $ git commit -a -m 'finished the new footer [issue 53]'
+ [iss53]: created ad82d7a: "finished the new footer [issue 53]"
+ 1 files changed, 1 insertions(+), 0 deletions(-)
+
+Insert 18333fig0315.png
+Figure 3-15. Your iss53 branch can move forward independently.
+
+It’s worth noting here that the work you did in your `hotfix` branch is not contained in the files in your `iss53` branch. If you need to pull it in, you can merge your `master` branch into your `iss53` branch by running `git merge master`, or you can wait to integrate those changes until you decide to pull the `iss53` branch back into `master` later.
+
+### Basic Merging ###
+
+Suppose you’ve decided that your issue #53 work is complete and ready to be merged into your `master` branch. In order to do that, you’ll merge in your `iss53` branch, much like you merged in your `hotfix` branch earlier. All you have to do is check out the branch you wish to merge into and then run the `git merge` command:
+
+ $ git checkout master
+ $ git merge iss53
+ Merge made by recursive.
+ README | 1 +
+ 1 files changed, 1 insertions(+), 0 deletions(-)
+
+This looks a bit different than the `hotfix` merge you did earlier. In this case, your development history has diverged from some older point. Because the commit on the branch you’re on isn’t a direct ancestor of the branch you’re merging in, Git has to do some work. In this case, Git does a simple three-way merge, using the two snapshots pointed to by the branch tips and the common ancestor of the two. Figure 3-16 highlights the three snapshots that Git uses to do its merge in this case.
+
+Insert 18333fig0316.png
+Figure 3-16. Git automatically identifies the best common-ancestor merge base for branch merging.
+
+Instead of just moving the branch pointer forward, Git creates a new snapshot that results from this three-way merge and automatically creates a new commit that points to it (see Figure 3-17). This is referred to as a merge commit and is special in that it has more than one parent.
+
+It’s worth pointing out that Git determines the best common ancestor to use for its merge base; this is different than CVS or Subversion (before version 1.5), where the developer doing the merge has to figure out the best merge base for themselves. This makes merging a heck of a lot easier in Git than in these other systems.
+
+Insert 18333fig0317.png
+Figure 3-17. Git automatically creates a new commit object that contains the merged work.
+
+Now that your work is merged in, you have no further need for the `iss53` branch. You can delete it and then manually close the ticket in your ticket-tracking system:
+
+ $ git branch -d iss53
+
+### Basic Merge Conflicts ###
+
+Occasionally, this process doesn’t go smoothly. If you changed the same part of the same file differently in the two branches you’re merging together, Git won’t be able to merge them cleanly. If your fix for issue #53 modified the same part of a file as the `hotfix`, you’ll get a merge conflict that looks something like this:
+
+ $ git merge iss53
+ Auto-merging index.html
+ CONFLICT (content): Merge conflict in index.html
+ Automatic merge failed; fix conflicts and then commit the result.
+
+Git hasn’t automatically created a new merge commit. It has paused the process while you resolve the conflict. If you want to see which files are unmerged at any point after a merge conflict, you can run `git status`:
+
+ [master*]$ git status
+ index.html: needs merge
+ # On branch master
+ # Changed but not updated:
+ # (use "git add <file>..." to update what will be committed)
+ # (use "git checkout -- <file>..." to discard changes in working directory)
+ #
+ # unmerged: index.html
+ #
+
+Anything that has merge conflicts and hasn’t been resolved is listed as unmerged. Git adds standard conflict-resolution markers to the files that have conflicts, so you can open them manually and resolve those conflicts. Your file contains a section that looks something like this:
+
+ <<<<<<< HEAD:index.html
+ <div id="footer">contact : email.support@github.com</div>
+ =======
+ <div id="footer">
+ please contact us at support@github.com
+ </div>
+ >>>>>>> iss53:index.html
+
+This means the version in HEAD (your master branch, because that was what you had checked out when you ran your merge command) is the top part of that block (everything above the `=======`), while the version in your `iss53` branch looks like everything in the bottom part. In order to resolve the conflict, you have to either choose one side or the other or merge the contents yourself. For instance, you might resolve this conflict by replacing the entire block with this:
+
+ <div id="footer">
+ please contact us at email.support@github.com
+ </div>
+
+This resolution has a little of each section, and I’ve fully removed the `<<<<<<<`, `=======`, and `>>>>>>>` lines. After you’ve resolved each of these sections in each conflicted file, run `git add` on each file to mark it as resolved. Staging the file marks it as resolved in Git.
+If you want to use a graphical tool to resolve these issues, you can run `git mergetool`, which fires up an appropriate visual merge tool and walks you through the conflicts:
+
+ $ git mergetool
+ merge tool candidates: kdiff3 tkdiff xxdiff meld gvimdiff opendiff emerge vimdiff
+ Merging the files: index.html
+
+ Normal merge conflict for 'index.html':
+ {local}: modified
+ {remote}: modified
+ Hit return to start merge resolution tool (opendiff):
+
+If you want to use a merge tool other than the default (Git chose `opendiff` for me in this case because I ran the command on a Mac), you can see all the supported tools listed at the top after “merge tool candidates”. Type the name of the tool you’d rather use. In Chapter 7, we’ll discuss how you can change this default value for your environment.
+
+After you exit the merge tool, Git asks you if the merge was successful. If you tell the script that it was, it stages the file to mark it as resolved for you.
+
+You can run `git status` again to verify that all conflicts have been resolved:
+
+ $ git status
+ # On branch master
+ # Changes to be committed:
+ # (use "git reset HEAD <file>..." to unstage)
+ #
+ # modified: index.html
+ #
+
+If you’re happy with that, and you verify that everything that had conflicts has been staged, you can type `git commit` to finalize the merge commit. The commit message by default looks something like this:
+
+ Merge branch 'iss53'
+
+ Conflicts:
+ index.html
+ #
+ # It looks like you may be committing a MERGE.
+ # If this is not correct, please remove the file
+ # .git/MERGE_HEAD
+ # and try again.
+ #
+
+You can modify that message with details about how you resolved the merge if you think it would be helpful to others looking at this merge in the future — why you did what you did, if it’s not obvious.
+
+## Branch Management ##
+
+Now that you’ve created, merged, and deleted some branches, let’s look at some branch-management tools that will come in handy when you begin using branches all the time.
+
+The `git branch` command does more than just create and delete branches. If you run it with no arguments, you get a simple listing of your current branches:
+
+ $ git branch
+ iss53
+ * master
+ testing
+
+Notice the `*` character that prefixes the `master` branch: it indicates the branch that you currently have checked out. This means that if you commit at this point, the `master` branch will be moved forward with your new work. To see the last commit on each branch, you can run `git branch –v`:
+
+ $ git branch -v
+ iss53 93b412c fix javascript issue
+ * master 7a98805 Merge branch 'iss53'
+ testing 782fd34 add scott to the author list in the readmes
+
+Another useful option to figure out what state your branches are in is to filter this list to branches that you have or have not yet merged into the branch you’re currently on. The useful `--merged` and `--no-merged` options have been available in Git since version 1.5.6 for this purpose. To see which branches are already merged into the branch you’re on, you can run `git branch –merged`:
+
+ $ git branch --merged
+ iss53
+ * master
+
+Because you already merged in `iss53` earlier, you see it in your list. Branches on this list without the `*` in front of them are generally fine to delete with `git branch -d`; you’ve already incorporated their work into another branch, so you’re not going to lose anything.
+
+To see all the branches that contain work you haven’t yet merged in, you can run `git branch --no-merged`:
+
+ $ git branch --no-merged
+ testing
+
+This shows your other branch. Because it contains work that isn’t merged in yet, trying to delete it with `git branch -d` will fail:
+
+ $ git branch -d testing
+ error: The branch 'testing' is not an ancestor of your current HEAD.
+ If you are sure you want to delete it, run 'git branch -D testing'.
+
+If you really do want to delete the branch and lose that work, you can force it with `-D`, as the helpful message points out.
+
+## Branching Workflows ##
+
+Now that you have the basics of branching and merging down, what can or should you do with them? In this section, we’ll cover some common workflows that this lightweight branching makes possible, so you can decide if you would like to incorporate it into your own development cycle.
+
+### Long-Running Branches ###
+
+Because Git uses a simple three-way merge, merging from one branch into another multiple times over a long period is generally easy to do. This means you can have several branches that are always open and that you use for different stages of your development cycle; you can merge regularly from some of them into others.
+
+Many Git developers have a workflow that embraces this approach, such as having only code that is entirely stable in their `master` branch — possibly only code that has been or will be released. They have another parallel branch named develop or next that they work from or use to test stability — it isn’t necessarily always stable, but whenever it gets to a stable state, it can be merged into `master`. It’s used to pull in topic branches (short-lived branches, like your earlier `iss53` branch) when they’re ready, to make sure they pass all the tests and don’t introduce bugs.
+
+In reality, we’re talking about pointers moving up the line of commits you’re making. The stable branches are farther down the line in your commit history, and the bleeding-edge branches are farther up the history (see Figure 3-18).
+
+Insert 18333fig0318.png
+Figure 3-18. More stable branches are generally farther down the commit history.
+
+It’s generally easier to think about them as work silos, where sets of commits graduate to a more stable silo when they’re fully tested (see Figure 3-19).
+
+Insert 18333fig0319.png
+Figure 3-19. It may be helpful to think of your branches as silos.
+
+You can keep doing this for several levels of stability. Some larger projects also have a `proposed` or `pu` (proposed updates) branch that has integrated branches that may not be ready to go into the `next` or `master` branch. The idea is that your branches are at various levels of stability; when they reach a more stable level, they’re merged into the branch above them.
+Again, having multiple long-running branches isn’t necessary, but it’s often helpful, especially when you’re dealing with very large or complex projects.
+
+### Topic Branches ###
+
+Topic branches, however, are useful in projects of any size. A topic branch is a short-lived branch that you create and use for a single particular feature or related work. This is something you’ve likely never done with a VCS before because it’s generally too expensive to create and merge branches. But in Git it’s common to create, work on, merge, and delete branches several times a day.
+
+You saw this in the last section with the `iss53` and `hotfix` branches you created. You did a few commits on them and deleted them directly after merging them into your main branch. This technique allows you to context-switch quickly and completely — because your work is separated into silos where all the changes in that branch have to do with that topic, it’s easier to see what has happened during code review and such. You can keep the changes there for minutes, days, or months, and merge them in when they’re ready, regardless of the order in which they were created or worked on.
+
+Consider an example of doing some work (on `master`), branching off for an issue (`iss91`), working on it for a bit, branching off the second branch to try another way of handling the same thing (`iss91v2`), going back to your master branch and working there for a while, and then branching off there to do some work that you’re not sure is a good idea (`dumbidea` branch). Your commit history will look something like Figure 3-20.
+
+Insert 18333fig0320.png
+Figure 3-20. Your commit history with multiple topic branches.
+
+Now, let’s say you decide you like the second solution to your issue best (`iss91v2`); and you showed the `dumbidea` branch to your coworkers, and it turns out to be genius. You can throw away the original `iss91` branch (losing commits C5 and C6) and merge in the other two. Your history then looks like Figure 3-21.
+
+Insert 18333fig0321.png
+Figure 3-21. Your history after merging in dumbidea and iss91v2.
+
+It’s important to remember when you’re doing all this that these branches are completely local. When you’re branching and merging, everything is being done only in your Git repository — no server communication is happening.
+
+## Remote Branches ##
+
+Remote branches are references to the state of branches on your remote repositories. They’re local branches that you can’t move; they’re moved automatically whenever you do any network communication. Remote branches act as bookmarks to remind you where the branches on your remote repositories were the last time you connected to them.
+
+They take the form `(remote)/(branch)`. For instance, if you wanted to see what the `master` branch on your `origin` remote looked like as of the last time you communicated with it, you would check the `origin/master` branch. If you were working on an issue with a partner and they pushed up an `iss53` branch, you might have your own local `iss53` branch; but the branch on the server would point to the commit at `origin/iss53`.
+
+This may be a bit confusing, so let’s look at an example. Let’s say you have a Git server on your network at `git.ourcompany.com`. If you clone from this, Git automatically names it `origin` for you, pulls down all its data, creates a pointer to where its `master` branch is, and names it `origin/master` locally; and you can’t move it. Git also gives you your own `master` branch starting at the same place as origin’s `master` branch, so you have something to work from (see Figure 3-22).
+
+Insert 18333fig0322.png
+Figure 3-22. A Git clone gives you your own master branch and origin/master pointing to origin’s master branch.
+
+If you do some work on your local master branch, and, in the meantime, someone else pushes to `git.ourcompany.com` and updates its master branch, then your histories move forward differently. Also, as long as you stay out of contact with your origin server, your `origin/master` pointer doesn’t move (see Figure 3-23).
+
+Insert 18333fig0323.png
+Figure 3-23. Working locally and having someone push to your remote server makes each history move forward differently.
+
+To synchronize your work, you run a `git fetch origin` command. This command looks up which server origin is (in this case, it’s `git.ourcompany.com`), fetches any data from it that you don’t yet have, and updates your local database, moving your `origin/master` pointer to its new, more up-to-date position (see Figure 3-24).
+
+Insert 18333fig0324.png
+Figure 3-24. The git fetch command updates your remote references.
+
+To demonstrate having multiple remote servers and what remote branches for those remote projects look like, let’s assume you have another internal Git server that is used only for development by one of your sprint teams. This server is at `git.team1.ourcompany.com`. You can add it as a new remote reference to the project you’re currently working on by running the `git remote add` command as we covered in Chapter 2. Name this remote `teamone`, which will be your shortname for that whole URL (see Figure 3-25).
+
+Insert 18333fig0325.png
+Figure 3-25. Adding another server as a remote.
+
+Now, you can run `git fetch teamone` to fetch everything server has that you don’t have yet. Because that server is a subset of the data your `origin` server has right now, Git fetches no data but sets a remote branch called `teamone/master` to point to the commit that `teamone` has as its `master` branch (see Figure 3-26).
+
+Insert 18333fig0326.png
+Figure 3-26. You get a reference to teamone’s master branch position locally.
+
+### Pushing ###
+
+When you want to share a branch with the world, you need to push it up to a remote that you have write access to. Your local branches aren’t automatically synchronized to the remotes you write to — you have to explicitly push the branches you want to share. That way, you can use private branches for work you don’t want to share, and push up only the topic branches you want to collaborate on.
+
+If you have a branch named `serverfix` that you want to work on with others, you can push it up the same way you pushed your first branch. Run `git push (remote) (branch)`:
+
+ $ git push origin serverfix
+ Counting objects: 20, done.
+ Compressing objects: 100% (14/14), done.
+ Writing objects: 100% (15/15), 1.74 KiB, done.
+ Total 15 (delta 5), reused 0 (delta 0)
+ To git@github.com:schacon/simplegit.git
+ * [new branch] serverfix -> serverfix
+
+This is a bit of a shortcut. Git automatically expands the `serverfix` branchname out to `refs/heads/serverfix:refs/heads/serverfix`, which means, “Take my serverfix local branch and push it to update the remote’s serverfix branch.” We’ll go over the `refs/heads/` part in detail in Chapter 9, but you can generally leave it off. You can also do `git push origin serverfix:serverfix`, which does the same thing — it says, “Take my serverfix and make it the remote’s serverfix.” You can use this format to push a local branch into a remote branch that is named differently. If you didn’t want it to be called `serverfix` on the remote, you could instead run `git push origin serverfix:awesomebranch` to push your local `serverfix` branch to the `awesomebranch` branch on the remote project.
+
+The next time one of your collaborators fetches from the server, they will get a reference to where the server’s version of `serverfix` is under the remote branch `origin/serverfix`:
+
+ $ git fetch origin
+ remote: Counting objects: 20, done.
+ remote: Compressing objects: 100% (14/14), done.
+ remote: Total 15 (delta 5), reused 0 (delta 0)
+ Unpacking objects: 100% (15/15), done.
+ From git@github.com:schacon/simplegit
+ * [new branch] serverfix -> origin/serverfix
+
+It’s important to note that when you do a fetch that brings down new remote branches, you don’t automatically have local, editable copies of them. In other words, in this case, you don’t have a new `serverfix` branch — you only have an `origin/serverfix` pointer that you can’t modify.
+
+To merge this work into your current working branch, you can run `git merge origin/serverfix`. If you want your own `serverfix` branch that you can work on, you can base it off your remote branch:
+
+ $ git checkout -b serverfix origin/serverfix
+ Branch serverfix set up to track remote branch refs/remotes/origin/serverfix.
+ Switched to a new branch "serverfix"
+
+This gives you a local branch that you can work on that starts where `origin/serverfix` is.
+
+### Tracking Branches ###
+
+Checking out a local branch from a remote branch automatically creates what is called a _tracking branch_. Tracking branches are local branches that have a direct relationship to a remote branch. If you’re on a tracking branch and type git push, Git automatically knows which server and branch to push to. Also, running `git pull` while on one of these branches fetches all the remote references and then automatically merges in the corresponding remote branch.
+
+When you clone a repository, it generally automatically creates a `master` branch that tracks `origin/master`. That’s why `git push` and `git pull` work out of the box with no other arguments. However, you can set up other tracking branches if you wish — ones that don’t track branches on `origin` and don’t track the `master` branch. The simple case is the example you just saw, running `git checkout -b [branch] [remotename]/[branch]`. If you have Git version 1.6.2 or later, you can also use the `--track` shorthand:
+
+ $ git checkout --track origin/serverfix
+ Branch serverfix set up to track remote branch refs/remotes/origin/serverfix.
+ Switched to a new branch "serverfix"
+
+To set up a local branch with a different name than the remote branch, you can easily use the first version with a different local branch name:
+
+ $ git checkout -b sf origin/serverfix
+ Branch sf set up to track remote branch refs/remotes/origin/serverfix.
+ Switched to a new branch "sf"
+
+Now, your local branch sf will automatically push to and pull from origin/serverfix.
+
+### Deleting Remote Branches ###
+
+Suppose you’re done with a remote branch — say, you and your collaborators are finished with a feature and have merged it into your remote’s `master` branch (or whatever branch your stable codeline is in). You can delete a remote branch using the rather obtuse syntax `git push [remotename] :[branch]`. If you want to delete your `serverfix` branch from the server, you run the following:
+
+ $ git push origin :serverfix
+ To git@github.com:schacon/simplegit.git
+ - [deleted] serverfix
+
+Boom. No more branch on your server. You may want to dog-ear this page, because you’ll need that command, and you’ll likely forget the syntax. A way to remember this command is by recalling the `git push [remotename] [localbranch]:[remotebranch]` syntax that we went over a bit earlier. If you leave off the `[localbranch]` portion, then you’re basically saying, “Take nothing on my side and make it be `[remotebranch]`.”
+
+## Rebasing ##
+
+In Git, there are two main ways to integrate changes from one branch into another: the `merge` and the `rebase`. In this section you’ll learn what rebasing is, how to do it, why it’s a pretty amazing tool, and in what cases you won’t want to use it.
+
+### The Basic Rebase ###
+
+If you go back to an earlier example from the Merge section (see Figure 3-27), you can see that you diverged your work and made commits on two different branches.
+
+Insert 18333fig0327.png
+Figure 3-27. Your initial diverged commit history.
+
+The easiest way to integrate the branches, as we’ve already covered, is the `merge` command. It performs a three-way merge between the two latest branch snapshots (C3 and C4) and the most recent common ancestor of the two (C2), creating a new snapshot (and commit), as shown in Figure 3-28.
+
+Insert 18333fig0328.png
+Figure 3-28. Merging a branch to integrate the diverged work history.
+
+However, there is another way: you can take the patch of the change that was introduced in C3 and reapply it on top of C4. In Git, this is called _rebasing_. With the `rebase` command, you can take all the changes that were committed on one branch and replay them on another one.
+
+In this example, you’d run the following:
+
+ $ git checkout experiment
+ $ git rebase master
+ First, rewinding head to replay your work on top of it...
+ Applying: added staged command
+
+It works by going to the common ancestor of the two branches (the one you’re on and the one you’re rebasing onto), getting the diff introduced by each commit of the branch you’re on, saving those diffs to temporary files, resetting the current branch to the same commit as the branch you are rebasing onto, and finally applying each change in turn. Figure 3-29 illustrates this process.
+
+Insert 18333fig0329.png
+Figure 3-29. Rebasing the change introduced in C3 onto C4.
+
+At this point, you can go back to the master branch and do a fast-forward merge (see Figure 3-30).
+
+Insert 18333fig0330.png
+Figure 3-30. Fast-forwarding the master branch.
+
+Now, the snapshot pointed to by C3 is exactly the same as the one that was pointed to by C5 in the merge example. There is no difference in the end product of the integration, but rebasing makes for a cleaner history. If you examine the log of a rebased branch, it looks like a linear history: it appears that all the work happened in series, even when it originally happened in parallel.
+
+Often, you’ll do this to make sure your commits apply cleanly on a remote branch — perhaps in a project to which you’re trying to contribute but that you don’t maintain. In this case, you’d do your work in a branch and then rebase your work onto `origin/master` when you were ready to submit your patches to the main project. That way, the maintainer doesn’t have to do any integration work — just a fast-forward or a clean apply.
+
+Note that the snapshot pointed to by the final commit you end up with, whether it’s the last of the rebased commits for a rebase or the final merge commit after a merge, is the same snapshot — it’s only the history that is different. Rebasing replays changes from one line of work onto another in the order they were introduced, whereas merging takes the endpoints and merges them together.
+
+### More Interesting Rebases ###
+
+You can also have your rebase replay on something other than the rebase branch. Take a history like Figure 3-31, for example. You branched a topic branch (`server`) to add some server-side functionality to your project, and made a commit. Then, you branched off that to make the client-side changes (`client`) and committed a few times. Finally, you went back to your server branch and did a few more commits.
+
+Insert 18333fig0331.png
+Figure 3-31. A history with a topic branch off another topic branch.
+
+Suppose you decide that you want to merge your client-side changes into your mainline for a release, but you want to hold off on the server-side changes until it’s tested further. You can take the changes on client that aren’t on server (C8 and C9) and replay them on your master branch by using the `--onto` option of `git rebase`:
+
+ $ git rebase --onto master server client
+
+This basically says, “Check out the client branch, figure out the patches from the common ancestor of the `client` and `server` branches, and then replay them onto `master`.” It’s a bit complex; but the result, shown in Figure 3-32, is pretty cool.
+
+Insert 18333fig0332.png
+Figure 3-32. Rebasing a topic branch off another topic branch.
+
+Now you can fast-forward your master branch (see Figure 3-33):
+
+ $ git checkout master
+ $ git merge client
+
+Insert 18333fig0333.png
+Figure 3-33. Fast-forwarding your master branch to include the client branch changes.
+
+Let’s say you decide to pull in your server branch as well. You can rebase the server branch onto the master branch without having to check it out first by running `git rebase [basebranch] [topicbranch]` — which checks out the topic branch (in this case, `server`) for you and replays it onto the base branch (`master`):
+
+ $ git rebase master server
+
+This replays your `server` work on top of your `master` work, as shown in Figure 3-34.
+
+Insert 18333fig0334.png
+Figure 3-34. Rebasing your server branch on top of your master branch.
+
+Then, you can fast-forward the base branch (`master`):
+
+ $ git checkout master
+ $ git merge server
+
+You can remove the `client` and `server` branches because all the work is integrated and you don’t need them anymore, leaving your history for this entire process looking like Figure 3-35:
+
+ $ git branch -d client
+ $ git branch -d server
+
+Insert 18333fig0335.png
+Figure 3-35. Final commit history.
+
+### The Perils of Rebasing ###
+
+Ahh, but the bliss of rebasing isn’t without its drawbacks, which can be summed up in a single line:
+
+**Do not rebase commits that you have pushed to a public repository.**
+
+If you follow that guideline, you’ll be fine. If you don’t, people will hate you, and you’ll be scorned by friends and family.
+
+When you rebase stuff, you’re abandoning existing commits and creating new ones that are similar but different. If you push commits somewhere and others pull them down and base work on them, and then you rewrite those commits with `git rebase` and push them up again, your collaborators will have to re-merge their work and things will get messy when you try to pull their work back into yours.
+
+Let’s look at an example of how rebasing work that you’ve made public can cause problems. Suppose you clone from a central server and then do some work off that. Your commit history looks like Figure 3-36.
+
+Insert 18333fig0336.png
+Figure 3-36. Clone a repository, and base some work on it.
+
+Now, someone else does more work that includes a merge, and pushes that work to the central server. You fetch them and merge the new remote branch into your work, making your history look something like Figure 3-37.
+
+Insert 18333fig0337.png
+Figure 3-37. Fetch more commits, and merge them into your work.
+
+Next, the person who pushed the merged work decides to go back and rebase their work instead; they do a `git push --force` to overwrite the history on the server. You then fetch from that server, bringing down the new commits.
+
+Insert 18333fig0338.png
+Figure 3-38. Someone pushes rebased commits, abandoning commits you’ve based your work on.
+
+At this point, you have to merge this work in again, even though you’ve already done so. Rebasing changes the SHA-1 hashes of these commits so to Git they look like new commits, when in fact you already have the C4 work in your history (see Figure 3-39).
+
+Insert 18333fig0339.png
+Figure 3-39. You merge in the same work again into a new merge commit.
+
+You have to merge that work in at some point so you can keep up with the other developer in the future. After you do that, your commit history will contain both the C4 and C4' commits, which have different SHA-1 hashes but introduce the same work and have the same commit message. If you run a `git log` when your history looks like this, you’ll see two commits that have the same author date and message, which will be confusing. Furthermore, if you push this history back up to the server, you’ll reintroduce all those rebased commits to the central server, which can further confuse people.
+
+If you treat rebasing as a way to clean up and work with commits before you push them, and if you only rebase commits that have never been available publicly, then you’ll be fine. If you rebase commits that have already been pushed publicly, and people may have based work on those commits, then you may be in for some frustrating trouble.
+
+## Summary ##
+
+We’ve covered basic branching and merging in Git. You should feel comfortable creating and switching to new branches, switching between branches and merging local branches together. You should also be able to share your branches by pushing them to a shared server, working with others on shared branches and rebasing your branches before they are shared.
View
710 fr/04-git-server/01-chapter4.markdown
@@ -0,0 +1,710 @@
+# Git on the Server #
+
+At this point, you should be able to do most of the day-to-day tasks for which you’ll be using Git. However, in order to do any collaboration in Git, you’ll need to have a remote Git repository. Although you can technically push changes to and pull changes from individuals’ repositories, doing so is discouraged because you can fairly easily confuse what they’re working on if you’re not careful. Furthermore, you want your collaborators to be able to access the repository even if your computer is offline — having a more reliable common repository is often useful. Therefore, the preferred method for collaborating with someone is to set up an intermediate repository that you both have access to, and push to and pull from that. We’ll refer to this repository as a "Git server"; but you’ll notice that it generally takes a tiny amount of resources to host a Git repository, so you’ll rarely need to use an entire server for it.
+
+Running a Git server is simple. First, you choose which protocols you want your server to communicate with. The first section of this chapter will cover the available protocols and the pros and cons of each. The next sections will explain some typical setups using those protocols and how to get your server running with them. Last, we’ll go over a few hosted options, if you don’t mind hosting your code on someone else’s server and don’t want to go through the hassle of setting up and maintaining your own server.
+
+If you have no interest in running your own server, you can skip to the last section of the chapter to see some options for setting up a hosted account and then move on to the next chapter, where we discuss the various ins and outs of working in a distributed source control environment.
+
+A remote repository is generally a _bare repository_ — a Git repository that has no working directory. Because the repository is only used as a collaboration point, there is no reason to have a snapshot checked out on disk; it’s just the Git data. In the simplest terms, a bare repository is the contents of your project’s `.git` directory and nothing else.
+
+## The Protocols ##
+
+Git can use four major network protocols to transfer data: Local, Secure Shell (SSH), Git, and HTTP. Here we’ll discuss what they are and in what basic circumstances you would want (or not want) to use them.
+
+It’s important to note that with the exception of the HTTP protocols, all of these require Git to be installed and working on the server.
+
+### Local Protocol ###
+
+The most basic is the _Local protocol_, in which the remote repository is in another directory on disk. This is often used if everyone on your team has access to a shared filesystem such as an NFS mount, or in the less likely case that everyone logs in to the same computer. The latter wouldn’t be ideal, because all your code repository instances would reside on the same computer, making a catastrophic loss much more likely.
+
+If you have a shared mounted filesystem, then you can clone, push to, and pull from a local file-based repository. To clone a repository like this or to add one as a remote to an existing project, use the path to the repository as the URL. For example, to clone a local repository, you can run something like this:
+
+ $ git clone /opt/git/project.git
+
+Or you can do this:
+
+ $ git clone file:///opt/git/project.git
+
+Git operates slightly differently if you explicitly specify `file://` at the beginning of the URL. If you just specify the path, Git tries to use hardlinks or directly copy the files it needs. If you specify `file://`, Git fires up the processes that it normally uses to transfer data over a network which is generally a lot less efficient method of transferring the data. The main reason to specify the `file://` prefix is if you want a clean copy of the repository with extraneous references or objects left out — generally after an import from another version-control system or something similar (see Chapter 9 for maintenance tasks). We’ll use the normal path here because doing so is almost always faster.
+
+To add a local repository to an existing Git project, you can run something like this:
+
+ $ git remote add local_proj /opt/git/project.git
+
+Then, you can push to and pull from that remote as though you were doing so over a network.
+
+#### The Pros ####
+
+The pros of file-based repositories are that they’re simple and they use existing file permissions and network access. If you already have a shared filesystem to which your whole team has access, setting up a repository is very easy. You stick the bare repository copy somewhere everyone has shared access to and set the read/write permissions as you would for any other shared directory. We’ll discuss how to export a bare repository copy for this purpose in the next section, “Getting Git on a Server.”
+
+This is also a nice option for quickly grabbing work from someone else’s working repository. If you and a co-worker are working on the same project and they want you to check something out, running a command like `git pull /home/john/project` is often easier than them pushing to a remote server and you pulling down.
+
+#### The Cons ####
+
+The cons of this method are that shared access is generally more difficult to set up and reach from multiple locations than basic network access. If you want to push from your laptop when you’re at home, you have to mount the remote disk, which can be difficult and slow compared to network-based access.
+
+It’s also important to mention that this isn’t necessarily the fastest option if you’re using a shared mount of some kind. A local repository is fast only if you have fast access to the data. A repository on NFS is often slower than the repository over SSH on the same server, allowing Git to run off local disks on each system.
+
+### The SSH Protocol ###
+
+Probably the most common transport protocol for Git is SSH. This is because SSH access to servers is already set up in most places — and if it isn’t, it’s easy to do. SSH is also the only network-based protocol that you can easily read from and write to. The other two network protocols (HTTP and Git) are generally read-only, so even if you have them available for the unwashed masses, you still need SSH for your own write commands. SSH is also an authenticated network protocol; and because it’s ubiquitous, it’s generally easy to set up and use.
+
+To clone a Git repository over SSH, you can specify ssh:// URL like this:
+
+ $ git clone ssh://user@server:project.git
+
+Or you can not specify a protocol — Git assumes SSH if you aren’t explicit:
+
+ $ git clone user@server:project.git
+
+You can also not specify a user, and Git assumes the user you’re currently logged in as.
+
+#### The Pros ####
+
+The pros of using SSH are many. First, you basically have to use it if you want authenticated write access to your repository over a network. Second, SSH is relatively easy to set up — SSH daemons are commonplace, many network admins have experience with them, and many OS distributions are set up with them or have tools to manage them. Next, access over SSH is secure — all data transfer is encrypted and authenticated. Last, like the Git and Local protocols, SSH is efficient, making the data as compact as possible before transferring it.
+
+#### The Cons ####
+
+The negative aspect of SSH is that you can’t serve anonymous access of your repository over it. People must have access to your machine over SSH to access it, even in a read-only capacity, which doesn’t make SSH access conducive to open source projects. If you’re using it only within your corporate network, SSH may be the only protocol you need to deal with. If you want to allow anonymous read-only access to your projects, you’ll have to set up SSH for you to push over but something else for others to pull over.
+
+### The Git Protocol ###
+
+Next is the Git protocol. This is a special daemon that comes packaged with Git; it listens on a dedicated port (9418) that provides a service similar to the SSH protocol, but with absolutely no authentication. In order for a repository to be served over the Git protocol, you must create the `git-export-daemon-ok` file — the daemon won’t serve a repository without that file in it — but other than that there is no security. Either the Git repository is available for everyone to clone or it isn’t. This means that there is generally no pushing over this protocol. You can enable push access; but given the lack of authentication, if you turn on push access, anyone on the internet who finds your project’s URL could push to your project. Suffice it to say that this is rare.
+
+#### The Pros ####
+
+The Git protocol is the fastest transfer protocol available. If you’re serving a lot of traffic for a public project or serving a very large project that doesn’t require user authentication for read access, it’s likely that you’ll want to set up a Git daemon to serve your project. It uses the same data-transfer mechanism as the SSH protocol but without the encryption and authentication overhead.
+
+#### The Cons ####
+
+The downside of the Git protocol is the lack of authentication. It’s generally undesirable for the Git protocol to be the only access to your project. Generally, you’ll pair it with SSH access for the few developers who have push (write) access and have everyone else use `git://` for read-only access.
+It’s also probably the most difficult protocol to set up. It must run its own daemon, which is custom — we’ll look at setting one up in the “Gitosis” section of this chapter — it requires `xinetd` configuration or the like, which isn’t always a walk in the park. It also requires firewall access to port 9418, which isn’t a standard port that corporate firewalls always allow. Behind big corporate firewalls, this obscure port is commonly blocked.
+
+### The HTTP/S Protocol ###
+
+Last we have the HTTP protocol. The beauty of the HTTP or HTTPS protocol is the simplicity of setting it up. Basically, all you have to do is put the bare Git repository under your HTTP document root and set up a specific `post-update` hook, and you’re done (See Chapter 7 for details on Git hooks). At that point, anyone who can access the web server under which you put the repository can also clone your repository. To allow read access to your repository over HTTP, do something like this:
+
+ $ cd /var/www/htdocs/
+ $ git clone --bare /path/to/git_project gitproject.git
+ $ cd gitproject.git
+ $ mv hooks/post-update.sample hooks/post-update
+ $ chmod a+x hooks/post-update
+
+That’s all. The `post-update` hook that comes with Git by default runs the appropriate command (`git update-server-info`) to make HTTP fetching and cloning work properly. This command is run when you push to this repository over SSH; then, other people can clone via something like
+
+ $ git clone http://example.com/gitproject.git
+
+In this particular case, we’re using the `/var/www/htdocs` path that is common for Apache setups, but you can use any static web server — just put the bare repository in its path. The Git data is served as basic static files (see Chapter 9 for details about exactly how it’s served).
+
+It’s possible to make Git push over HTTP as well, although that technique isn’t as widely used and requires you to set up complex WebDAV requirements. Because it’s rarely used, we won’t cover it in this book. If you’re interested in using the HTTP-push protocols, you can read about preparing a repository for this purpose at `http://www.kernel.org/pub/software/scm/git/docs/howto/setup-git-server-over-http.txt`. One nice thing about making Git push over HTTP is that you can use any WebDAV server, without specific Git features; so, you can use this functionality if your web-hosting provider supports WebDAV for writing updates to your web site.
+
+#### The Pros ####
+
+The upside of using the HTTP protocol is that it’s easy to set up. Running the handful of required commands gives you a simple way to give the world read access to your Git repository. It takes only a few minutes to do. The HTTP protocol also isn’t very resource intensive on your server. Because it generally uses a static HTTP server to serve all the data, a normal Apache server can serve thousands of files per second on average — it’s difficult to overload even a small server.
+
+You can also serve your repositories read-only over HTTPS, which means you can encrypt the content transfer; or you can go so far as to make the clients use specific signed SSL certificates. Generally, if you’re going to these lengths, it’s easier to use SSH public keys; but it may be a better solution in your specific case to use signed SSL certificates or other HTTP-based authentication methods for read-only access over HTTPS.
+
+Another nice thing is that HTTP is such a commonly used protocol that corporate firewalls are often set up to allow traffic through this port.
+
+#### The Cons ####
+
+The downside of serving your repository over HTTP is that it’s relatively inefficient for the client. It generally takes a lot longer to clone or fetch from the repository, and you often have a lot more network overhead and transfer volume over HTTP than with any of the other network protocols. Because it’s not as intelligent about transferring only the data you need — there is no dynamic work on the part of the server in these transactions — the HTTP protocol is often referred to as a _dumb_ protocol. For more information about the differences in efficiency between the HTTP protocol and the other protocols, see Chapter 9.
+
+## Getting Git on a Server ##
+
+In order to initially set up any Git server, you have to export an existing repository into a new bare repository — a repository that doesn’t contain a working directory. This is generally straightforward to do.
+In order to clone your repository to create a new bare repository, you run the clone command with the `--bare` option. By convention, bare repository directories end in `.git`, like so:
+
+ $ git clone --bare my_project my_project.git
+ Initialized empty Git repository in /opt/projects/my_project.git/
+
+The output for this command is a little confusing. Since `clone` is basically a `git init` then a `git fetch`, we see some output from the `git init` part, which creates an empty directory. The actual object transfer gives no output, but it does happen. You should now have a copy of the Git directory data in your `my_project.git` directory.
+
+This is roughly equivalent to something like
+
+ $ cp -Rf my_project/.git my_project.git
+
+There are a couple of minor differences in the configuration file; but for your purpose, this is close to the same thing. It takes the Git repository by itself, without a working directory, and creates a directory specifically for it alone.
+
+### Putting the Bare Repository on a Server ###
+
+Now that you have a bare copy of your repository, all you need to do is put it on a server and set up your protocols. Let’s say you’ve set up a server called `git.example.com` that you have SSH access to, and you want to store all your Git repositories under the `/opt/git` directory. You can set up your new repository by copying your bare repository over:
+
+ $ scp -r my_project.git user@git.example.com:/opt/git
+
+At this point, other users who have SSH access to the same server which has read-access to the `/opt/git` directory can clone your repository by running
+
+ $ git clone user@git.example.com:/opt/git/my_project.git
+
+If a user SSHs into a server and has write access to the `/opt/git/my_project.git` directory, they will also automatically have push access. Git will automatically add group write permissions to a repository properly if you run the `git init` command with the `--shared` option.
+
+ $ ssh user@git.example.com
+ $ cd /opt/git/my_project.git
+ $ git init --bare --shared
+
+You see how easy it is to take a Git repository, create a bare version, and place it on a server to which you and your collaborators have SSH access. Now you’re ready to collaborate on the same project.
+
+It’s important to note that this is literally all you need to do to run a useful Git server to which several people have access — just add SSH-able accounts on a server, and stick a bare repository somewhere that all those users have read and write access to. You’re ready to go — nothing else needed.
+
+In the next few sections, you’ll see how to expand to more sophisticated setups. This discussion will include not having to create user accounts for each user, adding public read access to repositories, setting up web UIs, using the Gitosis tool, and more. However, keep in mind that to collaborate with a couple of people on a private project, all you _need_ is an SSH server and a bare repository.
+
+### Small Setups ###
+
+If you’re a small outfit or are just trying out Git in your organization and have only a few developers, things can be simple for you. One of the most complicated aspects of setting up a Git server is user management. If you want some repositories to be read-only to certain users and read/write to others, access and permissions can be a bit difficult to arrange.
+
+#### SSH Access ####
+
+If you already have a server to which all your developers have SSH access, it’s generally easiest to set up your first repository there, because you have to do almost no work (as we covered in the last section). If you want more complex access control type permissions on your repositories, you can handle them with the normal filesystem permissions of the operating system your server runs.
+
+If you want to place your repositories on a server that doesn’t have accounts for everyone on your team whom you want to have write access, then you must set up SSH access for them. We assume that if you have a server with which to do this, you already have an SSH server installed, and that’s how you’re accessing the server.
+
+There are a few ways you can give access to everyone on your team. The first is to set up accounts for everybody, which is straightforward but can be cumbersome. You may not want to run `adduser` and set temporary passwords for every user.
+
+A second method is to create a single 'git' user on the machine, ask every user who is to have write access to send you an SSH public key, and add that key to the `~/.ssh/authorized_keys` file of your new 'git' user. At that point, everyone will be able to access that machine via the 'git' user. This doesn’t affect the commit data in any way — the SSH user you connect as doesn’t affect the commits you’ve recorded.
+
+Another way to do it is to have your SSH server authenticate from an LDAP server or some other centralized authentication source that you may already have set up. As long as each user can get shell access on the machine, any SSH authentication mechanism you can think of should work.
+
+## Generating Your SSH Public Key ##
+
+That being said, many Git servers authenticate using SSH public keys. In order to provide a public key, each user in your system must generate one if they don’t already have one. This process is similar across all operating systems.
+First, you should check to make sure you don’t already have a key. By default, a user’s SSH keys are stored in that user’s `~/.ssh` directory. You can easily check to see if you have a key already by going to that directory and listing the contents:
+
+ $ cd ~/.ssh
+ $ ls
+ authorized_keys2 id_dsa known_hosts
+ config id_dsa.pub
+
+You’re looking for a pair of files named something and something.pub, where the something is usually `id_dsa` or `id_rsa`. The `.pub` file is your public key, and the other file is your private key. If you don’t have these files (or you don’t even have a `.ssh` directory), you can create them by running a program called `ssh-keygen`, which is provided with the SSH package on Linux/Mac systems and comes with the MSysGit package on Windows:
+
+ $ ssh-keygen
+ Generating public/private rsa key pair.
+ Enter file in which to save the key (/Users/schacon/.ssh/id_rsa):
+ Enter passphrase (empty for no passphrase):
+ Enter same passphrase again:
+ Your identification has been saved in /Users/schacon/.ssh/id_rsa.
+ Your public key has been saved in /Users/schacon/.ssh/id_rsa.pub.
+ The key fingerprint is:
+ 43:c5:5b:5f:b1:f1:50:43:ad:20:a6:92:6a:1f:9a:3a schacon@agadorlaptop.local
+
+First it confirms where you want to save the key (`.ssh/id_rsa`), and then it asks twice for a passphrase, which you can leave empty if you don’t want to type a password when you use the key.
+
+Now, each user that does this has to send their public key to you or whoever is administrating the Git server (assuming you’re using an SSH server setup that requires public keys). All they have to do is copy the contents of the `.pub` file and e-mail it. The public keys look something like this:
+
+ $ cat ~/.ssh/id_rsa.pub
+ ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAQEAklOUpkDHrfHY17SbrmTIpNLTGK9Tjom/BWDSU
+ GPl+nafzlHDTYW7hdI4yZ5ew18JH4JW9jbhUFrviQzM7xlELEVf4h9lFX5QVkbPppSwg0cda3
+ Pbv7kOdJ/MTyBlWXFCR+HAo3FXRitBqxiX1nKhXpHAZsMciLq8V6RjsNAQwdsdMFvSlVK/7XA
+ t3FaoJoAsncM1Q9x5+3V0Ww68/eIFmb1zuUFljQJKprrX88XypNDvjYNby6vw/Pb0rwert/En
+ mZ+AW4OZPnTPI89ZPmVMLuayrD2cE86Z/il8b+gw3r3+1nKatmIkjn2so1d01QraTlMqVSsbx
+ NrRFi9wrf+M7Q== schacon@agadorlaptop.local
+
+For a more in-depth tutorial on creating an SSH key on multiple operating systems, see the GitHub guide on SSH keys at `http://github.com/guides/providing-your-ssh-key`.
+
+## Setting Up the Server ##
+
+Let’s walk through setting up SSH access on the server side. In this example, you’ll use the `authorized_keys` method for authenticating your users. We also assume you’re running a standard Linux distribution like Ubuntu. First, you create a 'git' user and a `.ssh` directory for that user.
+
+ $ sudo adduser git
+ $ su git