Migrating from SVN to GitLab

Subversion (SVN) is a central version control system (VCS) while Git is a distributed version control system. There are some major differences between the two, for more information consult your favorite search engine.

概要

There are two approaches to SVN to Git migration:

  1. Git/SVN Mirror which:
    • Makes the GitLab repository to mirror the SVN project.
    • Git and SVN repositories are kept in sync; you can use either one.
    • Smoothens the migration process and allows to manage migration risks.
  2. Cut over migration which:
    • Translates and imports the existing data and history from SVN to Git.
    • Is a fire and forget approach, good for smaller teams.

Smooth migration with a Git/SVN mirror using SubGit

SubGit is a tool for a smooth, stress-free SVN to Git migration. It creates a writable Git mirror of a local or remote Subversion repository and that way you can use both Subversion and Git as long as you like. It requires access to your GitLab server as it talks with the Git repositories directly in a filesystem level.

SubGit prerequisites

  1. Install Oracle JRE 1.8 or newer. On Debian-based Linux distributions you can follow this article.
  2. Download SubGit from https://subgit.com/download.
  3. Unpack the downloaded SubGit zip archive to the /opt directory. The subgit command will be available at /opt/subgit-VERSION/bin/subgit.

SubGit configuration

The first step to mirror you SVN repository in GitLab is to create a new empty project which will be used as a mirror. For Omnibus installations the path to the repository will be located at /var/opt/gitlab/git-data/repositories/USER/REPO.git by default. For installations from source, the default repository directory will be /home/git/repositories/USER/REPO.git. For convenience, assign this path to a variable: 

GIT_REPO_PATH=/var/opt/gitlab/git-data/repositories/USER/REPOS.git

SubGit will keep this repository in sync with a remote SVN project. For convenience, assign your remote SVN project URL to a variable: 

SVN_PROJECT_URL=http://svn.company.com/repos/project

Next you need to run SubGit to set up a Git/SVN mirror. Make sure the following subgit command is ran on behalf of the same user that keeps ownership of GitLab Git repositories (by default git): 

subgit configure --layout auto $SVN_PROJECT_URL $GIT_REPO_PATH

Adjust authors and branches mappings, if necessary. Open with your favorite text editor: 

edit $GIT_REPO_PATH/subgit/authors.txt
edit $GIT_REPO_PATH/subgit/config

For more information regarding the SubGit configuration options, refer to SubGit’s documentation website.

Initial translation

Now that SubGit has configured the Git/SVN repositories, run subgit to perform the initial translation of existing SVN revisions into the Git repository: 

subgit install $GIT_REPO_PATH

After the initial translation is completed, the Git repository and the SVN project will be kept in sync by subgit - new Git commits will be translated to SVN revisions and new SVN revisions will be translated to Git commits. Mirror works transparently and does not require any special commands.

If you would prefer to perform one-time cut over migration with subgit, use the import command instead of install: 

subgit import $GIT_REPO_PATH

SubGit licensing

Running SubGit in a mirror mode requires a registration. Registration is free for open source, academic and startup projects.

SubGit support

For any questions related to SVN to GitLab migration with SubGit, you can contact the SubGit team directly at support@subgit.com.

Cut over migration with svn2git

If you are currently using an SVN repository, you can migrate the repository to Git and GitLab. We recommend a hard cut over - run the migration command once and then have all developers start using the new GitLab repository immediately. Otherwise, it’s hard to keep changing in sync in both directions. The conversion process should be run on a local workstation.

Install svn2git. On all systems you can install as a Ruby gem if you already have Ruby and Git installed. 

sudo gem install svn2git

On Debian-based Linux distributions you can install the native packages: 

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

Optionally, prepare an authors file so svn2git can map SVN authors to Git authors. If you choose not to create the authors file then commits will not be attributed to the correct GitLab user. Some users may not consider this a big issue while others will want to ensure they complete this step. If you choose to map authors you will be required to map every author that is present on changes in the SVN repository. If you don’t, the conversion will fail and you will have to update the author file accordingly. The following command will search through the repository and output a list of authors. 

svn log --quiet | grep -E "r[0-9]+ \| .+ \|" | cut -d'|' -f2 | sed 's/ //g' | sort | uniq

Use the output from the last command to construct the authors file. Create a file called authors.txt and add one mapping per line. 

janedoe = Jane Doe <janedoe@example.com>
johndoe = John Doe <johndoe@example.com>

If your SVN repository is in the standard format (trunk, branches, tags, not nested) the conversion is simple. For a non-standard repository see svn2git documentation. The following command will checkout the repository and do the conversion in the current working directory. Be sure to create a new directory for each repository before running the svn2git command. The conversion process will take some time. 

svn2git https://svn.example.com/path/to/repo --authors /path/to/authors.txt

If your SVN repository requires a username and password add the --username <username> and --password <password> flags to the above command. svn2git also supports excluding certain file paths, branches, tags, etc. See svn2git documentation or run svn2git --help for full documentation on all of the available options.

Create a new GitLab project, where you will eventually push your converted code. Copy the SSH or HTTP(S) repository URL from the project page. Add the GitLab repository as a Git remote and push all the changes. This will push all commits, branches and tags. 

git remote add origin git@gitlab.com:<group>/<project>.git
git push --all origin
git push --tags origin

Contribute to this guide

We welcome all contributions that would expand this guide with instructions on how to migrate from SVN and other version control systems.