Mix and match version control
LShift’s standard version control platform these days is Mercurial, but just before we adopted it, I started a project using Trac and Subversion, mostly because that’s what Trac does out of the box.
Later, we branched the project to add a large new project, and during that branch we converted from using ant to Maven and modularised the project, resulting in a lot of moved files. This made what we were doing on the branch a lot easier, but left us with a merge that subversion wasn’t capable of, even though we had used
to move all the files.
What was capable of the merge was Mercurial. I imported the whole subversion repository using
. See the convert extension documentation. It works exactly as described, but make sure you have 1.0.1 or later – I had problems with earlier versions.
The merge went reasonably well, so I was left with a merged version in a Mercurial repository. I was going to switch to using Mercurial, and its Trac integration, when I discovered that couldn’t cope with multiple repositories. The Trac instance was managing several different source projects, which would have to go into several mercurial repositories, which I couldn’t merge together in any satisfactory way.
There are several projects around to address this (I’ll probably cover them in another post), none of which are ready for production yet. I decided the most expedient thing would be to try and generate a patch for my merge, and apply it to the subversion repository.
A conventional patch would lose the version history of all the moved files, so I decided a git diff would do the job. You can certainly, with some patience, get git-svn to do this, and understand what it was doing. Lacking that patience, I wrote a script to do the job. It parses the git diff and deals with any directory creation needed, calls to
as required by the diff. It actually turns out to be a bit more work than I was expecting, so I’ve published it here.