Re: git symbolic-ref vs. reflog (vs. rebase)

[Jeff King <peff@peff.net>]

On Fri, Apr 29, 2011 at 04:00:11PM -0700, Junio C Hamano wrote:

> Jeff King <peff@peff.net> writes:
> 
> > I think every caller should be using "-m" these days.  I know we can't
> > _require_ it for historical reasons. But shouldn't symbolic-ref always
> > write a reflog entry? Even something like "we changed and I can't tell
> > you why" to cover older scripts that call symbolic-ref?
> 
> I think the particular instance Csaba saw in rebase may want to pass the
> reason why it flipped the HEAD.

Oh, definitely. I was thinking more for external scripts that we can't
fix.

> Flipping HEAD temporarily to another ref to do something, only to flip it
> back before giving the control back to the user, might be something a
> script may want to have a choice of not logging, so I am mildly negative
> on changing the command to unconditionally log empty entry without being
> told.

Yeah, that is a legitimate use case. But I suspect many scripts were
simply never updated after reflogs were introduced (or their authors)
were lazy, so they flip it once without a reflog, and then the next
well-behaved writer who comes along ends up writing a reflog entry that
shows a hole.

So it is a question of whether helping probably-broken users is worth
shutting off a legitimate use case. I also wonder how valuable that use
case is. As a user, I think I'd rather see _everything_ in the reflog,
even if the script-writer doesn't think it's important.

I don't know that it matters much in any case. We haven't had any bug
reports either way; and given the current behavior, one can always yell
at the script author to properly reflog.

> "update-ref" seems to write an empty entry even when not given an "-m"
> option, and we can view it as robbing a similar choice from the scripts.
> We might want to fix it.  I dunno.

I'm inclined to wait until somebody actually wants it. In the meantime
it helps users of old and/or broken scripts by providing an additional
checkpoint of state that might otherwise be missing.

-Peff