From: =?UTF-8?q?Emin=20=C3=96zata?= <eminozata@proton.me>

There is no way to change the message of a stash entry after the
fact.  The only option is dropping the entry and re-storing it by
hand, which moves it to the top of the stash list and gets fiddly
for deeper entries.

Add 'git stash rename <message> [<stash>]', defaulting to the
latest entry like the other subcommands do.  It reads the object id
and reflog message of the target entry and of the entries above it,
drops them all like 'git stash drop' would, and stores them back in
the same order, with the new message going to the target.  Position,
contents and the reflog chain stay as they were.

The command checks every entry it is about to rewrite and refuses
to start if one of them does not look like a stash commit, which
can only happen when refs/stash was written to by hand.  Finding
that out halfway through the sequence would lose entries.  Should a
write-back fail anyway, the entry's object id is reported so it can
be recovered with 'git stash store', and the command only reports
success when the reflog ended up in the requested state.

This was proposed before: in 2010, as a "git reflog update" command
that edited reflog entries in place [1].  When it came up again in
2013 [2], Junio rejected it on the grounds that reflogs are
append-only recovery logs, and that whoever really cares about a
stash message can pop and re-stash [3].  Michael Haggerty pointed
out in that thread that refs/stash does not fit the description:
its reflog is the primary data store for stash entries, and 'git
stash drop' rewrites it all the time [4].  So this patch stays away
from the reflog machinery entirely and does the suggested
pop-and-re-stash workaround mechanically, without the detour
through the working tree.

The sequence only works if entry positions hold still while it
runs, so the command takes index-based selectors (stash@{1}) and
rejects time-based ones.  It also refreshes the reflog timestamps
of the rewritten entries, and renaming stash@{n} costs n+1 reflog
deletions and ref updates.

[1] https://lore.kernel.org/git/20100620093142.GF24805@occam.hewgill.net/
[2] https://lore.kernel.org/git/loom.20130104T192132-16@post.gmane.org/
[3] https://lore.kernel.org/git/7vbod4tynt.fsf@alter.siamese.dyndns.org/
[4] https://lore.kernel.org/git/50ED2C78.1030300@alum.mit.edu/

Signed-off-by: Emin Özata <eminozata@proton.me>

Submitted-As: https://lore.kernel.org/git/pull.2180.git.1784190706028.gitgitgadget@gmail.com