Introduction

Git is a version control system that lets you:

• Work offline.
• Browse history locally.
• Serve your version of the project.
• Branch and merge cheaply.

Google Code natively speaks Subversion, but you can easily use Git during development. We focus on importing a complete Git repository from a Google Code project organized in the recommended fashion. The git-svn manpage thoroughly describes how to handle other cases such as nonstandard layouts, importing only a few revisions, sharing exported repositories, and so on.

1. Import

First perform the equivalent of a svn checkout. In an empty subdirectory, run:

 $ git svn clone --username your-name -s https://your-project.googlecode.com/svn
   # older versions of git: replace "-s" with "-Ttrunk -bbranches -ttags"

Like a Subversion checkout, you now have a local copy of your project. Unlike a Subversion checkout, you also have a local copy of the entire history of the project. Try:

 $ git log          # print summary of history
 $ git diff HEAD^^  # diff against two revisions ago
 $ gitk             # graphical history browser
 $ qgit             # Qt-based history browser

These read from local disk, and work even when you're offline.

2. Develop

You now have a fully fledged version control system at your fingertips. You can checkpoint locally. You can create, merge, and destroy branches cheaply. You can checkout long-lost ancient code. You can stockpile and reorganize your commits.

Any Git tutorial teaches these abilities. We'll content ourselves with simple examples.

First, the basics. Edit code as usual, but if you add or remove files, type:

 $ git add FILENAME...

or

 $ git rm FILENAME...

There's no need to inform Subversion as git-svn will do so later. In fact, we only talk to Subversion via git-svn, and never run pure svn commands.

The only other git command you must know is:

 $ git commit -a

which saves the current state of your project locally. You can see them with git log. Commit early and commit often!

Now for a couple of tricks. Let's say you've made several commits and suppose you want to undo the last one:

 $ git reset --hard HEAD^

Or suppose you want to get a certain file from five commits ago:

 $ git checkout HEAD~5 foo.c

We've barely scratched the surface. There are countless other features worth learning, particularly Git's extraordinary lightweight branches.

3. Update

Periodically, you should get online and fetch the latest changes from Google Code with:

 $ git svn rebase   # think "svn update"

4. Export

Submit your commits to Google Code with:

 $ git svn dcommit  # think "svn commit"

This converts each of your Git commits into Subversion commits and uploads them, provided your repository is up-to-date. To keep working, go back to step 2.

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