Re: git filter-branch --subdirectory-filter not working as expected, history of other folders is preserved

[Jeff King <peff@peff.net>]

On Mon, Oct 10, 2016 at 02:42:36PM +0100, Seaders Oloinsigh wrote:

> We have a git repository that looks like
> 
> sdk/
> android/
> ios/
> unity/
> windows/
> 
> Which we'd like to split into 4 repositories, 1 for each platform.  To
> start this process (for splitting android out), I ran,
> 
> git filter-branch -f --prune-empty --subdirectory-filter android -- --all

OK, so that should rewrite each ref to have only the contents of the
"android" directory at the top-level.

Note that filter-branch saves a copy of the old refs in refs/original.

> Which rewrote a ton of history and commits, and looked like it worked, but
> on closer inspection had left a ton of history behind.
> 
> If I run
> 
> git log --all -- unity/
> 
> It returns a list of commits that happened in the unity/ subfolder of the
> original root.

Here you asked for "--all", which includes refs/original. So you are
seeing the original, unwritten commits (and none of your new ones, of
course, because they do not have a unity/ directory!).

Try:

  git log --all --source -- unity

to see which ref each commit is coming from.

Or try:

  git log --branches --tags -- unity

to confirm that your branches and tags do not include that path.

Or just:

  git for-each-ref --format='delete %(refname)' refs/original |
  git update-ref --stdin

to get rid of the backup refs entirely.

-Peff