From: David Brown Date: Fri, 20 Jan 2012 23:33:35 GMT Subject: Re: [Q] Determing if a commit is reachable from the HEAD ? Message-ID: <20120120233335.GA20302@codeaurora.org> In-Reply-To: <7v7h0mfahx.fsf@alter.siamese.dyndns.org> On Fri, Jan 20, 2012 at 11:18:50AM -0800, Junio C Hamano wrote: > David Brown writes: > > > On Fri, Jan 20, 2012 at 03:13:58PM +0100, Andreas Schwab wrote: > >> Brian Foster writes: > >> > >> > In a script, how can I determine commit Y is reachable > >> > from the current HEAD ? > >> > >> test $(git merge-base HEAD Y) = $(git rev-parse Y) > > > > Almost. It works as long as there is only one merge base. You really > > need to check if $(git rev-parse Y) is one of $(git merge-base --all > > HEAD Y) > > Can you give us an example of a topology to which "merge-base --all HEAD Y" > gives more than one output and Y is still reachable from HEAD? > > It is my understanding that merge-base computation will give only Y and > nothing else when Y is reachable from HEAD. I also think this assumption > is used by some of the internal code in Git, and that is why I care. Hmm, I thought I'd convinced myself that this was possible. Now, I can't come up with a way of doing it that doesn't involve improper commits with earlier timestamps than their parents. Sorry about that, David -- Sent by an employee of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.