Unintelligible

Wednesday, July 30, 2008

Migrating a Subversion repository to a remote Git repository

Migrating an existing SVN repository to git is pretty easy; here’s a quick step-by-step guide (and reminder to myself).

Before we start, let’s make sure git and git-svn are installed:

$ sudo apt-get install git git-core git-svn

1. Getting the code out of Subversion

First, use git-svn to get a copy of the remote Subversion repository you want to migrate. For instance:

$ mkdir MyProjectSVN && cd MyProjectSVN
$ git init
$ git-svn clone --authors-file=git-svn-users.txt --stdlayout https://my.svn.repository.com/MyProject

A couple of words on these options:

  • clone gets a copy of the entire repository, including all commit history, tags and branches
  • –stdlayout tells git-svn that you have laid your SVN repository as per the SVN recommendations, namely with top-level folders for trunk, tags and branches. If not, you can specify the paths for these relative to the repository root using the –trunk, –tags and –branches switches respectively (instead of –stdlayout)
  • the –authors-file option allows you to map SVN users to git users, for the commit history; the file should be in this format:
    svnUserId = First Last

This process will take a little while, especially for large repositories. When that’s done, git-svn will have created a new MyProject folder containing the full repository.

We can verify its contents:

$ cd MyProjectSVN
$ ls -la
$ cat .git/config
[core]
    repositoryformatversion = 0
    filemode = true
    bare = false
    logallrefupdates = true
[svn-remote "svn"]
    url = https://my.svn.repository.com/MyProject
    fetch = trunk:refs/remotes/trunk
    branches = branches/*:refs/remotes/*
    tags = tags/*:refs/remotes/tags/*

Note that the location of our remote SVN repository is stored in the .git/config - this allows git-svn to commit any changes you make back to the main SVN repository if you want to (how to do this is well explained in the introduction to git-svn for Subversion deserters).

2. Creating a remote git repository

However, our aim is to replace our existing remote SVN repository with a remote git repository; to do so, we first need to create an empty git repository on the remote machine, which we will then upload the repository we just created locally. This assumes that git-core is installed on the remote machine:

$ ssh me@remote-machine.com
$me@remote>: mkdir git/MyProject.git
$me@remote>: cd git/MyProject.git
$me@remote>: git --bare init
$me@remote>: pwd
/home/me/git/MyProject.git
$me@remote>: exit

A few notes on this:

  • the –bare option passed into git init tells git that we just want the repository, not the files (it isn’t necessary to have git create and update the code files remotely; we just want it to manage the repository. The code files and the repository are held in two different places in git.)
  • Note the output of pwd - this will be the path we will use to access the remote repository from our local box.

3. Clone the local repository

Now that we have created the remote repository, we can upload our local repository to its remote location. First though, back on our local machine, we’ll clone the git repository we used to extract the data from SVN:

$ cd ..
$ mkdir MyProject && cd MyProject
$ git init MyProject
$ cd ..
$ git clone MyProjectSVN MyProject
$ rm -rf MyProjectSVN

This will ensure we have a clean repository without any leftover SVN information. Now, we need to tell git where the remote repository is located:

$ cd MyProject
$ git remote add origin ssh://me@remote-machine.com/home/me/git/MyProject.git

Here:

  • remote add: adds a remote location
  • origin: the name of the remote location

Next, we need to tell git who we are:

$ git config --add user.name "First Last"
$ git config --add user.email me@domain.com

Let’s have a quick look at our configuration:

$ cat .git/config
[core]
    repositoryformatversion = 0
    filemode = true
    bare = false
    logallrefupdates = true
[user]
    name = First Last
    email = me@domain.com
[remote "origin"]
    url = ssh://me@remote-machine.com/home/me/git/MyProject.git
    fetch = +refs/heads/*:refs/remotes/origin/*

Note the user information and the remote location have been added to the config file.

4. Uploading to the remote git repository

That should be it - we’re ready to upload the local repository to the remote location. It’s as simple as:

$ git push --all origin
  • git push –all origin : push the all the local branches and tags to the remote repository, creating new remote branches of the same name

This will upload the contents of the master branch to the origin remote repository. Let’s check that we also have any tags and branches from subversion:

$git branches -r
branch1
branch2
tags/tag1
tags/tag2
  • git branches -r: list all remote branches

5. Accessing our new remote git repository

The contents of our local git repository were retrieved from SVN; now that we’ve uploaded that to our new remote git repository, we can get rid of the intermediary local repository we were working on, and begin using with our remote git repository in earnest:

$ cd ..
$ rm -rf MyProject
$ mkdir MyProject && cd MyProject
$ git init
$ git config --add user.name "First Last"
$ git config --add user.email me@domain.com
$ git remote add origin ssh://me@remote-machine.com/home/me/git/MyProject.git
$ git pull origin master
$ git branch -a
* master
  origin/master
  origin/branch1
  origin/branch2
$ cat .git/config
[core]
    repositoryformatversion = 0
    filemode = true
    bare = false
    logallrefupdates = true
[user]
    name = First Last
    email = me@domain.com
[remote "origin"]
    url = ssh://me@remote-machine.com/home/me/git/MyProject.git
    fetch = +refs/heads/*:refs/remotes/origin/*

That’s it! We’ve just pulled the master branch from our remote git repository, and at this stage, we are ready to start working with git locally. Note that when we ask git to tell us about all of the branches it knows about, it mentions all of the branches and tags from SVN as remote, but not local; this is because we only pulled the master branch from the remote repository.

We can now edit files, commit changes, and then push those changes to our remote repository; a good place for SVN users to start learning how to do this is the Git-SVN Crash Course

Note: if you have git-svn installed on the remote machine and the SVN repository is accessible from your remote machine, you can use git-svn to clone the repository from SVN directly on the remote machine using the –bare option (which gets just the repository, without the files). You can then use git pull to get a local copy once the remote information has been set up; this involves less steps, and would likely be a little quicker. I didn’t have access to git-svn remotely or the permissions to install it (shared hosting), so this wasn’t an option for me.

The following guides were helpful to me:
Setting up a new remote git repository - Toolman Tim
An introduction to git-svn for Subversion deserters
Converting a Subversion repository to git - Ruby Forums
Converting Subversion repositories to Git - Redline Software

posted by Nick at 9:02 pm - filed in linux  

1 Comment »

  1. [...] Unintelligible » Migrating a Subversion repository to a remote Git repository Migrating an existing SVN repository to git is pretty easy; here’s a quick step-by-step guide (tags: git svn git-svn migrating subversion repository repo) [...]

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