Keeping reflogs on branch deletion

[bdowning@lavos.net (Brian Downing)]

On Wed, Feb 13, 2008 at 07:43:21PM -0800, Junio C Hamano wrote:
> People often mistake that the safety of "branch -d" is to not
> lose the commit (i.e. not making it unreachable), but that is
> not the case.  That safety already exists in HEAD reflogs.
> 
> The "branch -d" safety is about not losing the particular point.
> The information we really are trying to protect is "this branch
> points at _that commit_", which is just as important if not
> more.

This actually brings up something I've been intending to ask.

When deleting a branch, is there any reason we can't add a deletion
entry into the reflog and keep the reflog around?  This would seem to be
a lot safer; I know I've been burned by expecting the reflog safety net
to be there, and surprised that it's not when I've deleted a branch.

I expect that the reflog entry would look something like this:

0000000000000000000000000000000000000000 4685dfedd47683a476e75166b5c273c0269b7e54 Brian Downing <bdowning@lavos.net> 1202996833 -0600   branch: Created from ubuntu-dapper
4685dfedd47683a476e75166b5c273c0269b7e54 0000000000000000000000000000000000000000 Brian Downing <bdowning@lavos.net> 1202996863 -0600   branch: Deleted

A couple of problems I've noticed that would have to be fixed for this
to work:

* git log -g (and anything else that can take a reflog) would have to be
  fixed or modified to allow for taking branches that no longer exist:

  :; ls .git/logs/refs/heads/foo
  .git/logs/refs/heads/foo
  :; git log -g foo
  fatal: ambiguous argument 'foo': unknown revision or path not in the working tree.
  Use '--' to separate paths from revisions

  My uneducated suspicion is that this may be somewhat hard.

* If the above did work, it would be nice for the deletion entry to
  result in a nice "branch was deleted" entry in log -g output.  Today,
  that entry is missing in its entirety.

-bcd