Hacking Corner

Most people probably already know that it’s possible to merge histories of multiple repositories by using the subtree merge strategy [1]. However, sometimes you also need to separate/decouple the history of a repository’s subdirectory into a stand-alone repository. This post outlines how.

In this example we decouple dokuwiki/lib/plugins/piwik from the dokuwiki repository.

$ git clone --no-hardlinks ~/projects/others/dokuwiki dokuwiki-piwik
$ cd dokuwiki-piwik
$ git filter-branch --subdirectory-filter lib/plugins/piwik HEAD
  # should list about as many commits as there are in the subdirectory
$ git status
# On branch master
# Your branch and 'origin/master' have diverged,
# and have 18 and 62 different commit(s) each, respectively.
#
nothing to commit (working directory clean)

Now some cleanup to get rid of the main repository objects (assuming you want that):

$ git remote rm origin
$ git show-ref
  # remove all the refs
$ git tag -l
  # remove all the tags
$ git gc --aggressive --prune=0

Also see stackoverflow.com for discussion about keeping branches and tags in the decoupled repository.

tips git, tips