How to Setup a Two Way Sync Between SVN and Git

Setup

1. Create a directory on your computer for the git repository (Ex. ~/git)
2. Download svn-migration-scripts.jar to your home directory (Ex. /Users/rwinkle or ~)
3. Open your Terminal
4. Run this command to verify you have all the appropriate software (git, svn, JRE). NOTE: On Mac you will get an error: “You appear to be running on a case-insensitive file-system. This is unsupported, and can result in data loss.” I ignored this message at my own peril.

   java -jar ~/svn-migration-scripts.jar verify

5. Change the directory to the folder created in step 1 “cd ~/git”
6. Create the author mapping file (authors.txt) from SVN to Git. SVN only has username whereas Git includes username and email. Run the following command:

   java -jar ~/svn-migration-scripts.jar authors https://mycompany.com/path/to/svn/repo > authors.txt

7. Open authors.txt in a text editor and update the the email address domain from mycompany.com to your particular domain. Here’s what my authors.txt file contained:

   fffff = fffff <fffff@aaaaa.com>
   sssss = sssss <sssss@aaaaa.com>
   lllll = lllll <lllll@aaaaa.com> 
   scmadmin = scmadmin <scmadm@aaaaa.com>
   rrrrrr = rrrrrr <rrrrr@aaaaa.com>

8. Clone the SVN repository to a local repository using git svn command

   git clone https://github.com/olsondigital/repo-1234
   cd repo-1234

    

   git svn clone --stdlayout --authors-file=authors.txt https://mycompany.com/path/to/svn/repo repo-1234

9. Update your local git user profile so that it is accurate and reflects your GitHub username and email

   computername:repo-1234 username$ git config --global --edit
   # This is Git's per-user configuration file.
   [user]
   # Please adapt and uncomment the following lines:
           name = winklerj
           email = robb.winkle@gmail.com

    

10. If you have an empty GitHub repo, create a README.md file with the following and commit it

    # My Title
    This repository is synced with the current SVN repository
    on a tracking branch svnsync-* where * is the SVN branch. For
    example svnsync-trunk

     

    git add README.md
    git commit -m "Initial commit"

     

11.  Create a branch to sync with an SVN branch. Use the naming convention svnsync-{svn_branch_name} where svn_branch_name is the branch name in SVN. For the initial sync it should be the latest release branch. You can have multiple git branches that map to the corresponding SVN branch. Below is just one example. (NEVER COMMIT DIRECTLY TO THIS BRANCH OR YOU WILL HAVE CONFLICTS)
    

    git branch --no-track svnsync-DEV_1_0_0_Release
    git checkout svnsync-DEV_1_10_0_Release

     

12. Initialize and fetch the SVN repository while the new branch is checked out. NOTE: The fetch timed out on me the first time I ran it. I ran it a second time and it completed.

    git svn init -s https://mycompany.com/path/to/svn/repo
    git svn fetch --authors-file=../authors.txt

     

13.  Set the author location so you don’t have to enter it each time when fetching

    git config svn-remote.svn.authorsfile ../authors.txt

     

14. Hard reset master to the branch specified 2 steps back (DEV_1_0_0_Release). This will now make the code from DEV_1_0_0_Release the current commit on master

    git reset --hard remotes/origin/DEV_1_0_0_Release

     

15. Switch to master, merge your SVN tracking branch into master, and push to the GitHub origin master branch

    git checkout master
    git reset --hard svnsync-DEV_1_0_0_Release
    git push origin master

     

16. You should now see the SVN code in the GitHub repository https://github.com/olsondigital/repo-1234
17. Create a develop branch off of master and push to origin

    git checkout master
    git checkout -b develop
    git push origin develop

     

18. Set develop to the default branch in GitHub

Setup Sync with a New SVN Release Branch

1. Perform step 11 in the previous section and create a tracking branch in git
2. Pull down SVN changes

   git svn fetch

3. Perform step 14 and 15 in the previous section and now your master branch should be on the new SVN branch

Syncing from SVN to Git

This is for keeping Git and SVN in sync. All changes from svn are going to be merged locally and staged to be pushed out to the Github repository.

1. Update the authors.txt file in the directory created in step 1 of setup (Ex. ~/git). This can be done manually or there are options described here: https://www.atlassian.com/git/tutorials/migrating-synchronize
2. Checkout the SVN tracking branch

   git checkout svnsync-DEV_1_0_0_Release

    

3. Fetch the latest changes from SVN

   git svn rebase

    

4. Switch to master and merge the SVN tracking branch

   git checkout master
   git merge svnsync-DEV_1_0_0_Release

    

5. Push the merged changes to GitHub origin master

   git push origin master

    

Note that these instructions were done on a OS X and branch naming conventions are based on gitflow.  The instructions may vary for Windows or different branching models.  Also the article mentions Github and git interchangeably.  These instructions were done against Github but can be used with any git repository.

Here are the pages I referenced to come up with this method of syncing

• https://www.atlassian.com/git/tutorials/migrating-prepare (Only using the author mapping part. This method will create a one way sync for migration NOT a two way sync)
• https://ben.lobaugh.net/blog/147853/creating-a-two-way-sync-between-a-github-repository-and-subversion