From: Junio C Hamano <gitster@pobox.com>
Date: Thu, 09 May 2013 17:08:24 GMT
Subject: Re: [PATCH 1/2] sha1_name.c: signal if @{-N} was a true branch nameor a detached head
Message-ID: <7vhaicaxo7.fsf@alter.siamese.dyndns.org>
In-Reply-To: <20130509064607.GA11985@sigill.intra.peff.net>

Jeff King <peff@peff.net> writes:

> Since the point of marking the detached HEAD is to turn off things like
> "@{-1}@{u}", we would want to be generous and err on the side of
> assuming it is a branch if it _might_ be one.

I am not sure X and Y mesh well in your "Since X, we would want Y".
It seems to argue for erring on the side of detached HEAD to me.

Checking the "from" name $HEX against old_sha1 is a local and cheap
measure I added there for the first level of disambiguation.  If
they do not match, we _know_ we didn't come back from a detached
HEAD state.

In order to err on the "favor branch when it could have been one",
you could additionally look for the reflog .git/logs/refs/heads/$HEX
when the "from" name $HEX matches old_sha1 (which is likely to be
detached, but it is possible that we were on the $HEX branch when
its tip was at $HEX) and making sure the tip of that $HEX branch
once used to be at $HEX at the time recorded for @{-N} in the HEAD
reflog in question.

That is far more expensive, though; I doubt it is worth doing.