Migrating a SVN repository to Git (Bitbucket)

This article explains how to migrate a SVN repository to Git. Although this guide uses BitBucket as the Git repository, you can easily adjust the steps to migrate to a different Git repository provider.

I was recently tasked to migrate a repository from SVN to Git (BitBucket). I have tried the the importer from BitBucket but it failed due to corruption in our SVN repository.

So I had no other alternative than to do things by hand. Below is the process I have used and some gotchas.

Authors

SVN stores just a username with every commit. So nikos could be one and Nikos could be another user. Git however stores also the email of the user and to make things work perfectly we need to create an authors.txt file which contains the mapping between the SVN users and the Git users.

NOTE The authors.txt file is not necessary for the migration. It only helps for the mapping between your current users (in your Git installation).

The format of the file is simple:

bash

captain = Captain America <cap@avengers.org>

If you have the file ready, skip the steps below. Alternatively you can generate the authors.txt file by running the following command in your SVN project folder:

bash

svn log -q | \
    awk -F '|' '/^r/ {sub("^ ", "", $2); sub(" $", "", $2); print $2" = "$2" <"$2">"}' | \
    sort -u > authors.txt

Conventions

The source SVN repository is called SVNSOURCE
The target GIT repository is called GITTARGET
The SVN URL is https://svn.avengers.org/svn

Commands

Create a work folder and cd into it

bash

mkdir source_repo
cd source_repo/

Initialize the Git repository and copy the authors file in it

bash

git svn init https://svn.avengers.org/svn/SVNSOURCE/ --stdlayout 
cp ../authors.txt .

Set up the authors mapping file in the config

bash

git config svn.authorsfile authors.txt

Check the config just in case

bash

git config --local --list

The output should be something like this:

bash

core.repositoryformatversion=0
core.filemode=true
core.bare=false
core.logallrefupdates=true
svn-remote.svn.url=https://svn.avengers.org/svn/SVNSOURCE
svn-remote.svn.fetch=trunk:refs/remotes/trunk
svn-remote.svn.branches=branches/*:refs/remotes/*
svn-remote.svn.tags=tags/*:refs/remotes/tags/*
svn.authorsfile=authors.txt

Get the data from SVN (rerun the command if there is a timeout or proxy error)

bash

git svn fetch

Check the status of the repository and the branches

bash

git status
git branch -a

Create the new bare work folder

bash

cd ..
mkdir source_bare
cd source_bare/

Initialize the bare folder and map the trunk

bash

git init --bare .
git symbolic-ref HEAD refs/heads/trunk

Return to the work folder

bash

cd ..
cd source_repo/

Add the bare repo as the remote and push the data to it

bash

git remote add bare ../source_bare/
git config remote.bare.push 'refs/remotes/*:refs/heads/*'
git push bare

Return to the bare work folder and check the branches

bash

cd ..
cd source_bare/
git branch

Rename trunk to master

bash

git branch -m trunk master

Note all the branches that are prefixed /tags/ and modify the lines below (as many times as necessary) to convert SVN tags to Git tags

bash

git tag 3.0.0 refs/heads/tags/3.0.0
...
git branch -D tags/3.0.0
...

Alternatively you can put the following in a script and run it:

bash

git for-each-ref --format='%(refname)' refs/heads/tags | \
cut -d / -f 4 | \
while read ref
do
  git tag "$ref" "refs/heads/tags/$ref";
  git branch -D "tags/$ref";
done

Check the branches and the new tags

bash

git br
git tags

Check the authors

bash

git log

Push the repository to BitBucket

bash

git push --mirror git@bitbucket.org:avengers/GITTARGET

Enjoy