From: Josh Boyer <jwboyer@gmail.com>
Date: Tue, 22 Sep 2015 19:10:42 GMT
Subject: Re: Specifying N revisions after the initial commit
Message-ID: <CA+5PVA6YWJizRjseeJ4EpRya0Mpyrv3DoNsB3=Gi=dOiAoDfHg@mail.gmail.com>
In-Reply-To: <20150922214037.b6b48059f051fcd4060a5a85@domain007.com>

On Tue, Sep 22, 2015 at 2:40 PM, Konstantin Khomoutov
<kostix+git@007spb.ru> wrote:
> On Tue, 22 Sep 2015 14:32:19 -0400
> Josh Boyer <jwboyer@gmail.com> wrote:
>
>> Please CC me as I'm not subscribed.
>>
>> I was hoping someone could help me with the revision shorthand to get
>> the commit sha of a commit N commits after the initial commit.
>
> What happens if right after the initial commit, there have been five
> branches created -- with no common commits except for the initial one?
>
> That's the core limitation of the data model Git uses (and arguably any
> other DVCS system): all commits form a directed acyclic graph.
> The "directed" in that construct means that child commits contain a
> link to their parent commit (or commits) but not vice-versa.

Hm.  It has been so long since I've looked at the underlying model and
git has proven to be so flexible on such a variety of things that I
guess I forgot it was constructed through a DAG.  The --reverse
parameter to git-log and git-rev-parse had left me hopeful.

> Hence, given any particular commit, you're able to trace all of its
> ancestry, but the reverse is not possible.

That makes sense.  I suppose I will have to resort to parsing output
of git-rev-list or something.  Thanks for the reminder.

josh