Re: [RFC/PATCH 1/2] rebuash - squash/rebase in a single step

From: Johannes Sixt <j6t@kdbg.org>
Date: Jul 2, 2019, 19:30 UTC
Message-ID: <e8a39f00-7f88-7c32-ac18-12f17faf2c72@kdbg.org>
In-Reply-To: <xmqqr2784alt.fsf@gitster-ct.c.googlers.com>

Am 02.07.19 um 19:20 schrieb Junio C Hamano:

Show 30 quoted lines

> Derrick Stolee <stolee@gmail.com> writes:
> 
>> On 7/1/2019 2:35 PM, Junio C Hamano wrote:
>>> Jeff King <peff@peff.net> writes:
>>>
>>>>> First, we create a (temporary) merge commit of both branches (M3)
>>>>>
>>>>> ------------
>>>>> 	R1---R2---R3---R4---R5---R6---R7---M3
>>>>> 	 \         \              \       /
>>>>> 	  F1---F2---M1---F3---F4---M2---F5
>>>>> ------------
>>>>>
>> ...
>>> If M3 merge is always easier to manage than incremental stepwise
>>> rebase of the topic, then doing the "git merge --reverse-squash"
>>> would be a saner interface and also conceptually simpler.
>>
>> I agree that this would be a better way to expose this behavior,
>> and likely the implementation could be very clean.
> 
> What I was sort-of hoping to get comments on was actually something
> else.
> 
> Would there be cases where the merge M3 gets unmanageably complex
> even if rebasing the feature commits one by one is relatively simple
> (and how often would that happen)?  "merge --squash" would not work
> well (and extending the command to merge in a different direction
> would not help) in such a situation, but "rebase -i" would work
> much better (and "imerge" would, too).

I've come across the situation occasionally. Once I have resolved a bunch of conflicts in M1 and M2, I think twice whether I should rebase individual commits; it is typically much more tedious.

A common situation is that a line is "A" in F1, "B" in F2, and "C" in R3; then I have to resolve ONE conflict in M1 ("<B=C>"), but with individual commits rebased on top of R3, I have two conflicts, "<C=A>" and "<AC=B>", neither of which is helped by rerere.

After merges M1 and M2, it is all a done deal, and M3 is typically a much simpler merge than the sum of conflicts incurred by the individual commits. I would generally not recommend a rebase in this situation.

But I wouldn't turn M3 into a squashed merged commit, either, as long as F1...F5 aren't messy.

-- Hannes