Subject: Re: [PATCH] Introduce git-mirror, a tool for exactly mirroring another repository.

From: Sergey Vlasov <[email-masked]>
Date: Wed, 1 Nov 2006 15:18:59 +0300

On Wed, 01 Nov 2006 02:08:08 +0100 Jakub Narebski wrote:

> Junio C Hamano wrote:
> > Sergey Vlasov <[email-masked]> writes:
> >> BTW, I was thinking about the possibility to save removed refs under,
> >> e.g., refs/old/`date -I`/; maybe even non-fast-forward refs could be
> >> saved there - this will ensure that no object will ever disappear from
> >> the mirror, no matter what is done on the master side.  Obviously, in
> >> this case remote refs like refs/old/* should be filtered.
> >
> > I do not think that belongs to git-mirror.  It might be better to
> > have that option in update-ref machinery so that you would even
> > be protected from a `git branch -d` ran by mistake.

I agree - this would be even better.

What name format should be used for such saved refs?  refs/old/`date -I`
is not unique enough; probably `date --utc +%Y.%m.%d-%H.%M.%S`?  And it
would be good if multiple refs which were deleted or modified in a
non-fast-forward way during a single operation (like git-mirror) would
be saved together - which may be tricky if they are saved at the lower
level (in update-ref).

Adding the fast-forward check into update-ref also does not look nice,
but this check is required for full safety.

> Perhaps just don't remove log when branch is deleted. I tend for example
> to be careful when reordering commits on a branch, and use git branch -f
> instead of deleting and recreating branch to not lose reflog.

Keeping the reflog does not help - reflog entries are not refs, and do
not keep the referenced objects live in the repository.  Therefore old
objects will be lost when the repository is repacked and pruned.

Also, the reflog really must be deleted together with the ref itself -
otherwise it may cause a file/directory conflict when another ref is
created.  Of course, if the ref is renamed instead of deleting, the
corresponding reflog may be renamed too.