Re: [FIXED PATCH] Make rebase save ORIG_HEAD if changing current branch

From: Junio C Hamano <gitster@pobox.com>
Date: Jul 7, 2008, 06:28 UTC
Message-ID: <7vbq1a8ay3.fsf@gitster.siamese.dyndns.org>
In-Reply-To: <803A3528-2451-4C5D-A48D-5E0C37B8E90E@silverinsanity.com>

Brian Gernhardt <benji@silverinsanity.com> writes:

> My final thought is that the rational ORIG_HEAD and when we set it is
> not clearly documented anywhere.  But I am currently out of time to
> work on git, so that patch won't be coming from me soon.

The idea behind ORIG_HEAD is to have an anchoring point before an operation that moves your HEAD in a drastic way. Think if it as a poor-man's reflog -- in fact it predates reflog.

That is why reset saves away the HEAD before it does its thing, so that you can easily say "Oops, I did not mean it -- reset ORIG_HEAD" to flip back to the previous state. Both a fast-forward merge and a real merge can be undone by resetting back to ORIG_HEAD.

So in that sense:

 (1) ORIG_HEAD is not strictly necessary these days, because we have
     reflogs;

 (2) Even then, it is handy and useful, and we could add ORIG_HEAD to more
     commands such as "git am" and "git rebase".