[fdo-internals] [mapguide-users] Migrating to Git from Subversion

Jackie Ng jumpinjackie at gmail.com
Tue May 26 04:47:12 PDT 2020

Hello Martin-Louis,

I'm cross-posting this to multiple mailing lists, hope this discussion
doesn't explode into spaghetti!!

There is no official git mirror. Un-officially, I have made some attempts
to create git mirrors:


But these repos are many months out of sync as I've stopped my personal AWS
EC2 instance that was doing the mirroring.

The problem with git mirroring right now is:

 1. MapGuide has svn:external links to CS-Map and Fusion repos. If we
mirror MapGuide to git, we have to mirror CS-Map and Fusion to git as well
at a bare minimum and translate svn:external references to their git
equivalents (submodules?)
    1.1. CS-Map has really large dictionary data files that break github's
repo file limits forcing me to use git-lfs for storing these files. But
git-lfs storage is a severely restricted service on GitHub's free tier.
Last I checked, I used up my free tier git-lfs quota just doing a single
force push of this repository!
    1.2. Git submodules are hell in my personal experience, but not using
submodules require developers having to set up CS-Map and Fusion source
trees manually within MapGuide's source tree.
 2. I have not been successful in coming up with a svn -> git conversion
scheme that allows commits or merged PRs in github to easily flow back into
SVN. This is probably because I've been cleaning out historical baggage
(eg. Commits of source/binary tarballs in LinuxApt/Installer) as part of
the svn -> git conversion process with bfg repo cleaner so a git clone is
not so bloated. But even on pristine converted git repos I could not
succesfully get git commits to flow back to its svn counterpart.

Now suppose we give up the notion of trying to have a bidirectional svn <->
git mirror and just bite the bullet and do a full blown one-way migration
(leaving the svn repos behind, and not have to worry about #2 above). Then
the problems become project management related.

 a) You preferably want buy-in from all PSCs involved in this one-way
migration, otherwise you're having to setup up and maintain "un-official"
git mirrors of all MapGuide upstream repos.
 b) For FDO particularly, I know Autodesk keeps maintaining a 4.2
commercial branch that I like to selectively merge useful commits from into
OS trunk and other OS branches on a semi-regular basis. One-way migrating
FDO to git would need Autodesk buy-in to continue their maintenance on the
migrated git repository.
 c) For CS-Map particularly, the dictionary file size limitations have to
be addressed. Preferably in a way that does not involve a paid git-lfs
storage plan.
 d) There's organizational questions around whether these migrated repos
should fall under the OSGeo github org or another github org.
 e) There's also setup/integration questions around OSGeo CLAs in these
repos as being an OSGeo project, we could not accept external pull requests
without confirmation (strongly-and-preferably automated) that the submitter
has signed and submitted an OSGeo CLA

Pardon the preceding wall of text, I had thoughts about git migration
brewing in my mind for a while but had not put anything to words since
nobody else had posed the git migration question until now.

Since you are also from Autodesk, it would probably be more effective to
for you to start this conversation with your colleagues who still commit
changes to these various projects "from within" to seek some consensus from
the Autodesk side as to whether it is worth moving to github in addition to
addressing some/all of the points I've raised. I wouldn't want to go all-in
on a one-way git migration only to find Autodesk still making commits to
the original SVN repos afterwards.

- Jackie



Is there a Git mirror for the MapGuide repo in Subversion at
https://svn.osgeo.org/? It would be great if this repository was on
https://github.com/OSGeo, for instance.

Martin-Louis Bright

Senior Software Engineer



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