Re: [RFC] Rebasing merges: a jorney to the ultimate solution (Road Clear)

From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Mar 8, 2018, 06:45 UTC
Message-ID: <nycvar.QRO.7.76.6.1803080741160.20700@ZVAVAG-6OXH6DA.rhebcr.pbec.zvpebfbsg.pbz>
In-Reply-To: <87ina8ymxs.fsf@javad.com>

Hi Sergey,

On Wed, 7 Mar 2018, Sergey Organov wrote:

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> Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:
> 
> > How can your approach -- which relies *very much* on having the
> > original parent commits -- not *require* that consistency check?
> 
> I don't understand what you mean, sorry. Could you please point me to
> the *require* you talk about in the original proposal?

Imagine a todo list that contains this line

	merge -C abcdef 123456

and now the user edits it (this is an interactive rebase, after all), adding another merge head:

	merge -C abcdef 987654 123456

Now your strategy would have a serious problem: to find the original version of 987654. If there was one.

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> > What would your approach (that still has no satisfyingly trivial
> > explanation, in my mind)
> 
> Here is one-liner: rebase sides of the merge commit and then 3-way
> merge them, using original merge commit as merge base.

But I already pointed out how that would undo a commit having been dropped.

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> > do if somebody edited a `merge` command and let it merge a completely
> > unrelated commit?
> 
> Don't see a problem, sorry. The method should still work, provided you have
> original merge commit and two new parents for the new merge.

That is assuming a lot. That is exactly what this consistency check is for, that I mentioned earlier, and which you listed as a downside of Phillip's strategy (forgetting that your strategy has the same downside, so...).

But I guess that you are still talking about the non-interactive version of the rebase, and missed that our conversation proceeded to the point where we want that same strategy to work *also* in the interactive version (and not have a completely different functionality depending whether you use --interactive or not)?

Ciao, Johannes