From: Junio C Hamano <gitster@pobox.com>
To: Jonathan Tan <jonathantanmy@google.com>
Cc: git@vger.kernel.org, jrnieder@gmail.com, sunshine@sunshineco.com
Subject: Re: [PATCH v2] fetch: remove fetch_if_missing=0
Date: Fri, 08 Nov 2019 16:40:02 +0900 [thread overview]
Message-ID: <xmqqmud6n7e5.fsf@gitster-ct.c.googlers.com> (raw)
In-Reply-To: <xmqqr22inagr.fsf@gitster-ct.c.googlers.com> (Junio C. Hamano's message of "Fri, 08 Nov 2019 15:33:40 +0900")
Junio C Hamano <gitster@pobox.com> writes:
> An interesting thing is that c32ca691c2^2 that moved the assignment
> to this big red switch variable around causes 3-way merge to fail in
> a miserable way. The "moving around" would involve removing from
> the same location as the rebased patch below removes, plus adding
> the assignment elsewhere, so "both sides removed the assignment from
> this hunk, so take that" would correctly leave the original assignment
> we see in the second hunk above removed, but fails to notice that
> the assignment made elsewhere (the result of "moving around" patch)
> is no longer needed, because "c32ca691c2^2 added one and this change
> does not do anything there, so take the addition" cleanly resolves
> to an incorrect merge result.
Total tangent. One frustrating thing is that we do this a bit
better at the tree level merge. After read-tree does three-way
merge at the tree level, what is passed to the merge-recursive
machinery has "side A added" and "side A removed" left unresolved,
so that the post-processing phase could try to match them up and say
"aha, side A moved that path elsewhere while side B just removed,
which is a conflict".
I wish if xdiff/xmerge.c could learn a similar trick, but the
necessary change feels quite involved, error prone and too magical.
prev parent reply other threads:[~2019-11-08 7:40 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-01 20:38 [PATCH] fetch: remove fetch_if_missing=0 Jonathan Tan
2019-11-01 22:05 ` Jonathan Nieder
2019-11-02 5:55 ` Junio C Hamano
2019-11-02 6:11 ` Eric Sunshine
2019-11-02 5:59 ` Junio C Hamano
2019-11-05 18:53 ` Jonathan Tan
2019-11-05 18:58 ` Jonathan Nieder
2019-11-05 18:56 ` [PATCH v2] " Jonathan Tan
2019-11-05 20:06 ` Eric Sunshine
2019-11-06 1:45 ` Junio C Hamano
2019-11-08 6:33 ` Junio C Hamano
2019-11-08 7:40 ` Junio C Hamano [this message]
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