Git and Github Basic Tutorial (1st draft)
Git and Github are two related tools for managing code, documentation, and related files. Used in concert, they facilitate version control - the process of editing files while maintaining a continous history of previous iterations of those files.
Git is a command-line tool for tracking changes in files; it also enables synchronization of files between a user's computer and a remote repository (sometimes abbreviated "repo") where files are hosted. Repositories are used to store files for a variety of reasons - backup/archiving, publication, and collaboration between multiple developers are among the most common use cases for respositories. The most well-known repository hosts are Github, Gitlab, and Bitbucket; this document is hosted on the andrew-leith/git-tutorial repository on Github.
Github is a web platform for hosting git repositories. On Github, a repository can be either public (that is, shared with all users), or private (shared only with users of a particular organization). A repository can contain multiple files, and in general, a given project is allocated its own repository. There are cases where a project is spread across multiple repositories, but it is generally bad practice to have multiple separate projects within a single repository. Github is the most popular platform for use with git, as well as the most commonly used host for source code in the world; thus, when people talk about using git or Github, they are typically addressing both of these tools collectively unless otherwise specified.
This document constitutes a brief 15-minute introduction to using git and Github with a specific focus on single-user repositories.
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To begin working with your new remote repository, you must synchronize it with a directory on your computer. Creating a local copy of a remote repository hosted on Github is simple - all that you need to do is click the large green button on the repository's main page labeled "Clone or download", copy the URL, and use the git clone command. git clone creates an exact copy of the remote repository in your terminal's working directory.
Once you've cloned the repository onto your computer, you can use the git pull command to update your local copy to match any changes that are made to the remote repository. For single-user repositories, this function is often unneeded, since nobody else will be making changes to your code; however, it is still useful in the event that you make changes to files using Github's web interface, as is often done when noticing a small mistake or typo. If you make a change remotely and do not pull it down, then make changes locally and attempt to push them, you will encounter a conflict where the software is unable to reconcile the two versions of the file(s) - depending on the extent of the conflict, this can range from a minor annoyance to a severe problem. New users would be well-advised to avoid letting this situation arise in the first place.
Files that have been cloned onto your computer can be edited like any other file. Editing the local copies does not, on its own, affect the files in the remote repository. To synchronize the remote files to match the local copies, you must use the git push command; however, before pushing changes, you must commit those changes - that is, you must designate which files you wish to push.