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| Original file line number | Diff line number | Diff line change |
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| hello | ||
| Welcome to the first lesson of the GitHub Learning course. This course | ||
| will lead you through a series of lessons that will demonstrate how to use | ||
| Git quickly and easily - many of the lessons will have screencasts that you | ||
| can watch as well, if you learn better that way. | ||
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| This chapter is about what Git is and why you should use it - just a quick | ||
| introduction before we start using it. | ||
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| Git is a **fast, open source, distributed version** control system that is quickly | ||
| replacing subversion in open source and corporate programming communities. | ||
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| ### version control system ### | ||
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| First off, Git is a _version control system_, a simple command line | ||
| tool for keeping a history on the state of your source code projects. You | ||
| use it as you might use something like Subversion, CVS or Perforce. | ||
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| You tell it to track files in your project and periodically commit the state | ||
| of the project when you want a saved point. Then you can share that history | ||
| with other developers for collaboration, merge between their work and yours, | ||
| and compare or revert to previous versions of the project or individual files. | ||
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| As it is primarily a command line tool, most of the examples in this course | ||
| will show the command line versions of the functions. We will be using a | ||
| recent version of Git (the 1.6 series) for the examples in this course. We | ||
| recommend upgrading to the 1.6 series if your version of Git is older - there | ||
| have been a number of UI improvements that make Git a bit easier to use. | ||
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| $ git --version | ||
| git version 1.6.1.2 | ||
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| If you need help with any of the commands, you can type '--help' and it will | ||
| show you the _man_ page. You can also type 'git help _command_' for the same thing. | ||
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| $ git log --help | ||
| $ git help log | ||
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| ### open source | ||
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| Git is an open source project, that has been active for several years and is | ||
| written mostly in C. | ||
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|  | ||
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| At any time you can get the full source code to analyze or improve upon. | ||
| To get a download of the source code, visit | ||
| [git-scm.com/download](http://git-scm.com/download). Git is licensed under | ||
| the GNU General Public License. | ||
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| ### offline and fast | ||
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| Git is fully distributed, which means that it can work almost entirely offline. | ||
| In stark contrast to VCS tools like Perforce or Subversion, Git does nearly all | ||
| of it's operations without needing a network connection, including history | ||
| viewing, difference viewing and commiting. | ||
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| This also means that Git is very fast compared to those systems partially due | ||
| to the fact that none of these operations has any dependency on network latency. | ||
| For example, take a look at how fast the simple 'log' command takes to run in | ||
| Git and in Subversion. | ||
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| [master]$ time git log > /dev/null | ||
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| real 0m0.352s | ||
| user 0m0.300s | ||
| sys 0m0.034s | ||
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| $ time svn log > /dev/null | ||
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| real 0m3.709s | ||
| user 0m0.482s | ||
| sys 0m0.168s | ||
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| Git at 0.3 seconds vs Subversion at 3.7 seconds. That is a difference of a | ||
| full order of magnatude. You'll find similar | ||
| differences with nearly any command comparison. For example, adding the popular | ||
| famfamfam icon set and committing them. Since you can seperate the commit from the | ||
| network 'push' in Git, this action takes a quarter of a second in Git, but 45 seconds | ||
| in Subversion. | ||
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| time 'git add icons; git commit -m "added icons"' | ||
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| real 0m0.273s | ||
| user 0m0.032s | ||
| sys 0m0.008s | ||
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| time 'svn add icons; svn commit -m "added icons"' | ||
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| real 0m45.276s | ||
| user 0m15.997s | ||
| sys 0m5.503s | ||
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| Even if you needed to push to a shared repository at that time as well, it still | ||
| takes far, far less time than Subversion. | ||
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| time git push | ||
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| real 0m6.219s | ||
| user 0m0.023s | ||
| sys 0m0.011s | ||
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| If you just want to commit and keep working, you're looking at a huge time | ||
| difference - one that severely changes your workflow. | ||
| Most commands in Git seem instantaneous - no more typing 'svn commit' and | ||
| then going for a cup of coffee. | ||
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| ### small (vs svn) ### | ||
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| Git is also very space efficient. For example, the Django project has mirrors | ||
| in several currently popular source control systems, and of all of them, the | ||
| Git clone is the smallest. | ||
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| $ du -d 1 -h | ||
| 108M ./django-bzr | ||
| 44M ./django-git | ||
| 53M ./django-hg | ||
| 53M ./django-svn | ||
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| Interestingly, it is even smaller than the Subversion checkout, which is pretty | ||
| amazing, considering that the Git clone contains the entire history of the project - | ||
| every version of every file back to the first commit, whereas the Subversion | ||
| checkout is just the last version of the project. | ||
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| ### snapshots, not changesets | ||
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| Unlike most other VCSs, Git is snapshot based. That is, instead of thinking | ||
| about and storing commit points as file based patches or deltas, it stores it | ||
| as a simple snapshot of what your project looked like when you committed. | ||
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| Commits, then, are simply objects that contain some metadata about the commit | ||
| (the message, author, date, etc), a pointer to a single snapshot of the project | ||
| and pointers to the commit(s) that came directly before it. Git's commit history | ||
| and data model is really just a directed graph - a simple series of snapshots. | ||
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|  | ||
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| Keeping this in mind is helpful when you're thinking about what Git will do | ||
| in a given situation. | ||
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| For a more in-depth examination of how Git stores data, checkout | ||
| [Git for Computer Scientists](http://eagain.net/articles/git-for-computer-scientists/). | ||
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||
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| ### cheap branching and easy merging | ||
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| Probably the most compelling feature of Git, since it often fundamentally | ||
| changes the way that many developers work, is Gits branching model. Instead | ||
| of the popular VCS branching method of simply cloning into a seperate directory | ||
| for a branch, Git lets you switch between branches in a single working directory. | ||
| Add to that the fact that creating and switching between branches is nearly | ||
| instant, not all of your branches need to be shared, and it's easy to stash | ||
| partially completed work - means that the way you work can be incredibly different. | ||
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| Instead of only having branches for major development line departures, Git | ||
| developers routinely create, merge and destroy multiple branches a week, or even | ||
| per day. Often each feature or bug you are working on can have its own branch, | ||
| merged in only when it is complete. This model allows you to experiment quickly, | ||
| easily and safely - without having to go through hoops to get back to where you | ||
| where. It enables and encourages a _non-linear_ development cycle, where you | ||
| can work on multiple lines of thought in parallel without them stepping on | ||
| each other. | ||
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| Many developers feel that this is so incredibly helpful and has changed | ||
| their workflow and productivity so much that they dub it the | ||
| ["killer feature"](http://www-cs-students.stanford.edu/~blynn/gitmagic/ch04.html) | ||
| of Git. | ||
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| ### installing git | ||
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| See the [Git Community Book](http://book.git-scm.com/2_installing_git.html) | ||
| for details on how to install Git on your particular operating system. | ||
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| ### resources | ||
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| For more information on Git, the homepage is at [git-scm.com](http://git-scm.com). | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,23 @@ | ||
| welcome to the first episode of the github learning course | ||
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| my name is scott chacon, and in this episode were going to learn what git is - just a quick introduction before we start using it | ||
|
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| Git is a fast, open source, distributed version control system that is quickly | ||
| replacing subversion in open source and corporate programming communities. | ||
|
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| # version control system | ||
| git --version | ||
| git help | ||
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| # open source | ||
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| # snapshots, not changesets | ||
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| # offline and fast | ||
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| # small (vs svn) | ||
| du -d 1 -h | ||
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| # cheap branching and easy merging | ||
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| # git-scm.com |
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,26 @@ | ||
| # setup | ||
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| git config --global user.name | ||
| git config --global user.name | ||
| git config user.name | ||
| cat ~/.gitconfig | ||
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| # init | ||
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| rails | ||
| git init | ||
| ls -la | ||
| git add . | ||
| git status | ||
| git commit (vim) | ||
| git config core.editor | ||
| git log | ||
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| # cloning | ||
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| git clone git://github.com/schacon/munger.git | ||
| cd munger | ||
| git log | ||
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| git clone http://github.com/schacon/munger.git | ||
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