The Right Stuff

Today we changed the URL of our Subversion server at work to a new domain. Subversion and TortoiseSVN offer a separate relocate command for that, which basically updates the local working copy metadata.

Not so for Git. Git keeps SVN metadata in two places: the commit log messages themselves which hold a git-svn-id entry for all commits that have been pushed to SVN, and in the .git/config file.

commit e82751b4872142679ba61e26fc0c57e97c698e8f
Author: agross 
Date:   Thu Jun 25 16:44:55 2009 +0000

    Adding FxCop to the code quality task

    git-svn-id: https://your.svn-server/svn/Crimson/trunk@67 8ed4a44c-bfb4-4748-a28a-fad9255c4788

[core]
	repositoryformatversion = 0
	filemode = false
	bare = false
	logallrefupdates = true
	ignorecase = true
[svn-remote "svn"]
	url = https://your.svn-server/svn/Crimson/trunk
	fetch = :refs/remotes/git-svn

To update the SVN URL it’s required to update the Git configuration file (an easy edit) and also to rewrite the commit log messages, updating the values of git-svn-id to reflect the new SVN server URL. The latter can be achieved with the git-filter-branch command which allows you to dissect the project history in interesting ways.

Having several local Git repositories to update, I went for the scripted solution. I found this article on how to change the SVN repository URL and added some scripting goodness to it (aside from fixing the syntactic errors). It worked pretty good for my ~10 repositories.

• You pass two arguments:
  • The old SVN URL, i.e. http://old.server
  • The new SVN URL, i.e. https://new.server
  • The old URL will be matched against git-svn-id entries with a regular expression, and the matched parts get replaced with the new URL.
• Rewrite the commit log messages, thus updating git-svn-id
• Create a backup copy of .git/config
• Replace the old SVN URL in .git/config
• Delete all metadata Git has aquired about SVN
• Rebase against SVN, recreating the SVN metadata

#!/bin/sh

# Must be called with two command-line args.
# Example: git-svn-relocate.sh http://old.server https://new.server
if [ $# -ne 2 ]  
then
  echo "Please invoke this script with two command-line arguments (old and new SVN URLs)."
  exit $E_NO_ARGS
fi  

# Prepare URLs for regex search and replace.
oldUrl=`echo $1 | awk '{gsub("[\\\.]", "\\\\\\\&");print}'`
newUrl=`echo $2 | awk '{gsub("[\\\&]", "\\\\\\\&");print}'`

filter="sed \"s|^git-svn-id: $oldUrl|git-svn-id: $newUrl|g\""
git filter-branch --msg-filter "$filter" -- --all

sed -i.backup -e "s|$oldUrl|$newUrl|g" .git/config

rm -rf .git/svn
git svn rebase