SVN to Git - Migrating just some branches

git, svn

I recently had to migrate a very old repository (about 15 years of history) from Subversion to Git. There are already
enough guides for this, but I had one extra requirement: clone just some branches.

I had to search in several places for all the information I needed to successfully migrate to Git (take a look at the
references at the end of this post), so I decided to share it all in one place.

The trick is to just init the repo and then manually select the branches.
I tried this on Windows (using CMDER as the terminal for UNIX commands). Let’s get started:

  1. Generate list of users from the SVN repo

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    svn log --xml | grep author | sort -u | perl -pe 's/.*>(.*?)<.*/$1 = /' | tee users.txt

  2. Clone svn repo from to git in the ‘tmp’ directory. Options:
    <repo_url>: the url of the svn repository
    -T trunk: specify your trunk path inside the svn repository
    --no-metadata: removes the SVN commit id from the commit’s history. Use this option only when you don’t need to update from SVN again.
    --no-minimize-url: allow the cloning of just subfolders

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    git svn init -T trunk <repo_url> --no-metadata --no-minimize-url tmp 
    # Go into created directory
    cd tmp

  3. Set the list of users for the commit authors

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    git config svn.authorsfile ../users.txt

  4. Update the ‘.git/config’ file to clone only specific branches.
    In this case, we’re going to clone only branches that match the pattern ‘feature*’

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    [svn-remote "svn"]
      noMetadata = 1
      url = <repo_url>
      fetch = trunk:refs/remotes/origin/trunk
      branches = branches/feature*:refs/remotes/origin/*  ## New line

  5. Get files from the SVN repository. Use an elevated command prompt (administrator rights)

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    # Be patient this could take several hours...
    git svn fetch

  6. Checkout the remote branches to keep them in the local repository. Below is an example of checking out the remote
    branches feature/foo and feature/bar 

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    # Make sure the remote branches you want are listed
    git branch -r

    # Checkout remote branches to keep them in the local repo
    # git checkout -b <local_branch> <remote_branch>
    git checkout -b feature/foo origin/feature/foo
    git checkout -b feature/bar origin/feature/bar

  7. Clone your git-svn repository into a clean Git repository:

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    cd ..
    git clone tmp dest_dir
    cd dest_dir

  8. Re-establish branches in the new Git repository

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    # git checkout -b <local_branch> <remote_branch>
    git checkout -b feature/foo origin/feature/foo
    git checkout -b feature/bar origin/feature/bar

  9. If you want to commit your local repository to an existing Git repository just set the new-repo-url

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    # Set new repo url
    git remote set-url origin <new-repo-url>

  10. Finally, push all branches to the new remote repository

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    git push --all

Another useful thing that I found is that if you don’t want to import all the history you could select the revisions to import
in step 5:

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git svn fetch -r $NUMBER:HEAD

References

Migrating SVN to Git

https://stackoverflow.com/a/3972103/2313246

http://blokspeed.net/blog/2010/09/converting-from-subversion-to-git/

Cloning a subfolder from the SVN repo

http://stackoverflow.com/questions/1453416/git-svn-clone-checkouts-wrong-repo

Selecting specific branches

http://stackoverflow.com/a/10173516/2313246

https://gist.github.com/trodrigues/1023167

Selecting revision range

https://git-scm.com/docs/git-svn#git-svn---revisionltarggt