====== Version Control With Git ======

Git is a version control system (like SVN and CSV). Among Git's many powerful features, these were most attractive to me:

  * Git makes it easy to create branches. The idea is that you have a master branch that's always in a "releasable" state, while you add new features on a separate branch. Once your new feature is finished, you merge the "new feature branch" into the master branch.
  * It's very easy to specify which files and directories git should ignore.
  * Git has a "bisect" feature which assists you in finding the specific revision where you unknowingly introduced a bug.

Please check this excellent tutorial for a high level introduction to the concepts behind Git: [[http://www.eecs.harvard.edu/~cduan/technical/git/|Understanding Git Conceptually]].






===== Setting Up a Remote Repository =====

Please Note: if you're using github.com as the remote repository server, just create a new repository on their website and follow their instructions.

The following procedure is taken from "[[http://toolmantim.com/articles/setting_up_a_new_remote_git_repository|Setting up a new remote git repository]]".

Set up the new bare repo on the remote server:

<code>
$ ssh myserver.com
Welcome to myserver.com!
$ mkdir /var/git/myapp.git && cd /var/git/myapp.git
$ git --bare init
Initialized empty Git repository in /var/git/myapp.git
$ exit
</code>

Please note: this assumes that you have a ''git'' user on your remote system who is authorized to log in through ssh. Also: use chmod and chown for the new directory!

On your local system, add the remote repository and push (omit ''git init'' if you already have a local git repository):

<code>
$ cd ~/Sites/myapp
$ git init
$ git remote add origin ssh://git@myserver.com/var/git/myapp.git
$ git push origin master
</code>

The original tutorial goes on to explain that you can specify the default remote repository by updating the git config file. However, when I checked my config file, it already contained the necessary settings for pushing and pulling to the default remote repository:

<code>
[branch "master"]
  remote = origin
  merge = refs/heads/master
</code>

Now you can simply ''git push'' and ''git pull''.


===== GIT Client under Windows (7) =====

To start using the GIT client for Windows you can use the following tutorial:
[[http://nathanj.github.com/gitguide/tour]].

When you get to the step **Pushing to a Remote Server** follow the following instructions:
  * Generate a private and public key
  * Specify your passphrase
  * Export the key using //Conversions// -> //Export OpenSSH key//
  * Save the file with the name //id_rsa// at the source location of your ssh. This is usually //C:\Users\[username]\.ssh//
  * Save the private key
  * Copy the public key to the clipboard. Do not save the public key as it saves in a different format than recognized at github.com
  * Add the public key to your account at github.com

Now follow the rest of the instructions as specified in the tutorial.


===== Adding foreign repositories as a plugin =====

You can use the command ''git submodule'' to populate a directory of your own project with a foreign repository.

Use cases: 
  * Adding a 3rd party Rails plugin to ''vendor/plugins''. 
  * Importing the Moodle Soda module into your ''mod'' directory.

Here's a tutorial: [[http://woss.name/2008/04/09/using-git-submodules-to-track-plugins/|Using git submodules to track plugins]], which explains everything in great detail. This tutorial is more concise: [[http://chrisjean.com/2009/04/20/git-submodules-adding-using-removing-and-updating/|Git Submodules: Adding, Using, Removing, Updating]].

The short version:

<code>
git submodule add git@github.com:solin-repo/soda public_html/local/soda
</code>

By default, git will checkout the master branch. If you need a different branch, just move into the submodule's directory and perform a 'normal' checkout:

<code>
git checkout moodle19
</code>


==== Making changes to a submodule ====

Go ahead, make the changes. Move into the submodule's directory and perform the exact same git commands that you would normally use to commit and push.


==== Cloning a submodule ====

To update your local repository with a remote submodule, do the following in the root of your git repository:

<code>
onno@mac-mini:~/php/kompas$ git submodule init
onno@mac-mini:~/php/kompas$ git submodule update
</code>

The result:

<code>
Initialized empty Git repository in /home/onno/php/kompas/public_html/mod/soda/.git/
remote: Counting objects: 337, done.
remote: Compressing objects: 100% (133/133), done.
remote: Total 337 (delta 238), reused 295 (delta 196)
Receiving objects: 100% (337/337), 259.68 KiB | 58 KiB/s, done.
Resolving deltas: 100% (238/238), done.
Submodule path 'public_html/mod/soda': checked out 'bf7200df78ff0d9a80494e30170ba04d12233e4d'
</code>


===== Various =====
==== How do I Make Git Ignore Mode Changes (chmod)? ====

From [[http://stackoverflow.com/questions/1580596/how-do-i-make-git-ignore-mode-changes-chmod|Stack Overflow]]:

git config core.filemode false

From git-config(1):
<code>
       core.fileMode
           If false, the executable bit differences between the index and the
           working copy are ignored; useful on broken filesystems like FAT.
           See git-update-index(1). True by default.
</code>


==== Ignore Things (Files, Dirs) Locally  ====

The ''.gitignore'' file is committed to the repository - everybody using the repo is affected by it. If you want to ignore things (files, directories) locally, use: **''.git/info/exclude''**. The ''exclude'' file uses the same directives / instructions as the .gitignore file.

===== Tags: local and remote =====

Adding a tag to a commit allows you to easily find the commit, even after a while. The tag will serve as a name that can be used besides the commit id.

To add a tag to a certain commit, you'll have to find the commit id. You can look them up with the following command:
<code>git log</code>

With the commit id you can create a new (local) tag:
<code>git tag tag_name commit_id</code>

To push the tag to the remote server you can use:
<code>git push --tags</code>


===== Adding Branches Remotely =====

Here's how to push a local branch to remote:

<code>
git push --set-upstream origin new-branch
</code>


===== Search a Repo Using Git Grep  =====

Use ''git grep'' to search a local repository. Example:

<code>
git grep 'function get_users'
</code>

To limit the search to a subtree, specify the directory outside the commandline options, using a 'pathspec':

<code>
git grep 'function get_users' -- 'mod/usermanager'
</code>

The '--' signals the end of the commandline arguments. Please **note the space between -- and the pathspec**.

ATTENTION: if you have a git submodule in your repo, git grep will not search this submodule. You have to descend into the submodule first.


===== Ignore files that are already in the repo  =====

To stop tracking a file that is currently tracked, use:

<code>git rm --cached $THE_FILE_NAME</code> (and add the file name in .gitignore or .git/info/exclude).

This will not delete the actual file.