Re: [PATCH] logging branch deletion to help recovering from mistakes

[Shawn Pearce <spearce@spearce.org>]

On Tue, Dec 7, 2010 at 9:06 AM, Jeff King <peff@peff.net> wrote:
> On Mon, Dec 06, 2010 at 10:28:53PM -0800, Junio C Hamano wrote:
>
>> > Should this special log be mentioned in git-update-ref.txt or
>> > gitrepository-layout.txt?
>>
>> Perhaps, but I wasn't sure if this patch itself is a good idea to begin
>> with.  Not the problem it tries to solve, but its approach.
>>
>> For example, this cannot be shown with "reflog show" or "log -g" due to
>> the way these frontends locate the reflog file to read (the logic wants to
>> have an underlying ref).
>
> Yeah, I think this is not _quite_ what people want in this area. A base
> requirement from past discussions, I think, is that the whole reflog of
> the deleted branch be saved rather than just the tip. And then "reflog
> show" would make a lot more sense on such saved reflogs.

Yup, that's what I recall too, folks (including myself) want to
save the reflog of the deleted branch, so it can be recovered if
the branch itself were to be recovered with an --undelete option.

> I'm not sure in practice how important that distinction is, as we are
> not saving deleted branch reflogs _at all_ right now, so the
> requirements are mostly speculation at this point.
>
> The most recent discussion I recall is this one:
>
>  http://thread.gmane.org/gmane.comp.version-control.git/144250/focus=145353
>
> where the general idea was to just keep deleted reflogs around, append
> to them if the branch was recreated, and use a consistent renaming
> scheme to avoid D/F naming conflicts (e.g., "foo" is a deleted ref, and
> you create "foo/bar").

Per check-ref-format, ref names cannot contain two dots.  We could
archive ref logs by renaming them, $GIT_DIR/logs/refs/heads/foo
becomes $GIT_DIR/logs/refs/heads/foo..deleted-1.  If foo is created
and deleted again, it becomes foo..deleted-2.

This still causes problems for git reflog show / git log -g because
they want a current ref to enumerate the log of.


A different approach might be to have $GIT_DIR/logs/refs/REF_ATTIC,
and special case that in git reflog show / git log -g.  When a
ref is deleted, append its entire log onto REF_ATTIC, between two
specially formatted marker lines.  When recovering a branch, copy
out the region from the REF_ATTIC log.

-- 
Shawn.