From: Junio C Hamano <gitster@pobox.com>
Date: Sun, 25 Jun 2017 22:22:58 GMT
Subject: Re: Getting first tag per branch for a commit
Message-ID: <xmqqd19r7lml.fsf@gitster.mtv.corp.google.com>
In-Reply-To: <xmqqy3sf7mxo.fsf@gitster.mtv.corp.google.com>

Junio C Hamano <gitster@pobox.com> writes:

> Orgad Shaneh <orgads@gmail.com> writes:
>
>> What I'd like to have is a way to tell the first tag per branch (or
>> per merge) that the commit appeared on.
>
>> I think that this can be done by filtering out tags that are connected
>> to already listed tags by first-parent link.
>
> Yes.  When one tag can be reached by another tag, then the former is
> definitely an earlier tag than the latter.
>
> A trivial way to compute it would require O(n^2) invocations of "git
> merge-base --is-ancestor".  Alternatively, I think you can perhaps
> use "git merge-base --independent".

Ah, forget the latter.  "independent" is about solving the opposite
use case--it is to cull the ones that can be reached by other tips.