git-svn-helpers 0.1b2dev

Command-line tools to make git-svn simple

git-svn-helpers is a collection of command line tools that greatly simplifies using git for svn repositories.

Its main goal is to make setting up a local git repository following an existing svn checkout a ‘no-brainer’.

It also addresses using a single git-svn repository for working on multiple checkouts of (usually) different branches and switching between them.

Basic usage (Example)

Executive summary:

> cd path/to/svn/repo
> gitify

Here’s a sample session:

> cd /tmp
> svn co https://svn.plone.org/svn/plone/plone.app.form/branches/1.1 plone.app.form
A    1.1/setup.py
...
Checked out revision 27228.
> cd plone.app.form
> gitify
No git repository found in /Users/tomster/.gitcache/.
Initiating cloning into cache.
Analyzing svn log...
Cloning https://svn.plone.org/svn/plone/plone.app.form/ from r10593:27155 into /Users/tomster/.gitcache/
Initialized empty Git repository in /Users/tomster/.gitcache/plone.app.form/.git/
...
Git branch 'local/1.1' is now following svn branch '1.1':
# On branch local/1.1
nothing to commit (working directory clean)
> git branch
* local/1.1
  master

Points to note:

• gitify limited the cloning to the revisions found in the svn log of the package root (here https://svn.plone.org/svn/plone/plone.app.form/). A big time saver, especially on large repositories (such as plone.collective)

• gitify created the git repository at ~/.gitcache not in place

• gitify created a local branch local/1.1 that follows the (remote) svn branch 1.1 and switched to it

Multiple check-outs

In practice you will often work with different local copies of a given repository, i.e. on trunk and on a feature branch. That’s when the .gitcache directory created above comes in handy. Let’s move our previous checkout out of the way and create a maintenance checkout that follows trunk:

> cd ..
> mkdir feature-branch
> mv plone.app.form feature-branch/
> mkdir maintenance
> cd maintenance/
> svn co https://svn.plone.org/svn/plone/plone.app.form/trunk plone.app.form
A    plone.app.form/setup.py
...
 U   plone.app.form
Checked out revision 27228.

What happens if we run gitify here?:

> cd plone.app.form/
> gitify
Git branch 'local/trunk' is now following svn branch 'trunk':
# On branch local/trunk
nothing to commit (working directory clean)

Notice, that this operation went much faster, as we now have used the existing git repository in the cache directory. This can be further evidenced by looking at the available local branches now:

> git branch
  local/1.1
* local/trunk
  master

Caveats

‘Recycling’ .git in this manner works (perhaps surprisingly) well in practice, but you need to keep the following in mind:

All checkouts share the same index!

Let’s take a look at what this means by switching back to our feature branch:

> cd ../../feature-branch/plone.app.form/
> git status
# On branch local/trunk
# Changed but not updated:
#   (use "git add/rm <file>..." to update what will be committed)
#   (use "git checkout -- <file>..." to discard changes in working directory)
#
#   modified:   docs/HISTORY.txt
...
#   deleted:    plone/app/form/kss/tests/test_kss.py
...
#
# Untracked files:
#   (use "git add <file>..." to include in what will be committed)
#
#   plone/app/form/tests/test_kss.py

Wohah! What happened is that .git now points to trunk and thus the status command shows the difference between that and our branch as local modifications, since that is what the filesystem represents. We can verify this by using subversions status command:

> svn st
<BLANKLINE>

Phew! All in order! But what to do with git? We’ve finished working on trunk and want to get back to our feature branch, but the git index is all wrong?! Simple: just re-run gitify:

> gitify
Git branch 'local/1.1' is now following svn branch '1.1':
# On branch local/1.1
nothing to commit (working directory clean)

Basically, that’s all you need to remember when working with multiple check-outs of the same package: Always run gitify when switching between check-outs!

TODO

‘Recycling’ git repositories with symlinks is sub-optimal. Ideally we would want to create local clones (IOW replace the symlink command with a git clone command). However, git clone currently doesn’t preserve the svn information of the source. That means we couldn’t dcommit from our cloned repository! Eventually, this should be fixed up-stream in git svn.