Re: [PATCH 2/2] diff-merges: introduce '-d' option

From: Junio C Hamano <gitster@pobox.com>
Date: Sep 15, 2023, 17:24 UTC
Message-ID: <xmqqzg1nfixw.fsf@gitster.g>
In-Reply-To: <87y1h8wbpo.fsf@osv.gnss.ru>

Sergey Organov <sorganov@gmail.com> writes:

> I don't see why desire to look at diff-to-first-parent on "side"
> branches is any different from desire to look at them on "primary"
> branch

Yeah, but that is not what I meant. The above argues for why "--diff-merges=first-parent" should exist independently from the "--first-parent" traversal *and* display option. I am not saying it should not exist.

But I view that the desire to look at any commits and its changes on the "side" branch at all *is* at odds with the wish to look at first-parent change for merge commits. Once you decide to look at first-parent change for a merge commit, then every change you see for each commit on the "side" branch, whether it is shown as first-parent diff or N pairwise diffs, is what you have already seen in the change in the merge commit, because "git log" goes newer to older, and the commits on the side branches appear after the merge that brings them to the mainline.

Making "log -d" mean "log --diff-merges=first-parent --patch" lets that less useful combination ("show first-parent patches but traverse side branches as well") squat on the short and sweet "-d" that could be used for more useful "log --first-parent --patch", which would also be more common and intuitive to users, and that is what I suspect will become problematic in the longer run.

Thanks.