experimenting with JGit and bitmaps

JGit has merged the bitmap work Colby and I were working on[1] and plans to ship it in JGit 2.4. The bitmaps are now stored in a separate ".bitmap" file alongside of a pack, making the entire system backward-compatible with git-core.

If you have Java and Maven installed you can try this out locally:

  $ git clone https://eclipse.googlesource.com/jgit/jgit
  # (fastest mirror of jgit is self-hosted here)

  $ cd jgit
  $ mvn package -Dmaven.test.skip=true -Dmaven.javadoc.skip=true

  $ org.eclipse.jgit.pgm/target/jgit debug-gc
  $ org.eclipse.jgit.pgm/target/jgit daemon --export-all --listen 127.0.0.1 . &
  $ git clone git://127.0.0.1/. tmp

I will be presenting some of this work at EclipseCon and ALMConnect.

JGit's GC implementation is still being worked on, hence the "debug-gc" name. I would only run it on a backup of a repository. Fortunately this is easy with Git. :-)

[1] http://thread.gmane.org/gmane.comp.version-control.git/206457
[2] http://www.eclipsecon.org/2013/sessions/scaling-jgit
    http://www.eclipsecon.org/2013/sessions/deploying-gerrit-code-review