Re: [SCRIPT/RFC 0/3] git-commit --onto-parent (three-way merge, no working tree file changes)

[Alexei Lozovsky <a.lozovsky@gmail.com>]

On Dec 9, 2017, at 01:54, Igor Djordjevic wrote:
> On 08/12/2017 17:24, Junio C Hamano wrote:
>> I'd rather do a quick fix-up on top (which ensures that at least the
>> fix-up works in the context of the tip), and then "rebase -i" to
>> move it a more appropriate place in the history (during which I have
>> a chance to ensure that the fix-up works in the context it is
>> intended to apply to).
> 
> Chris reported in this very topic[1] that sometimes, due to conflicts 
> with later commits, "checkout > commit > [checkout >] rebase --onto" 
> is "much easier to do", where "commit --fixup > rebase -i" "breaks" 
> (does not apply cleanly).

It was more of a rant about conflict resolution by rebase rather than
a concern about modification time of files. While I'd prefer git to
not touch the source tree unnecessarily, it's not really a big deal
for me if it does and some parts of the project need to be rebuilt.

The situations which tend to cause conflicts for me usually look
like this.

  ---A---B

Say, a file has this line added somewhere in commit A:

  +int some_function(); 

Then commit B adds another line:

   int some_function(); 
  +int another_function();

Then I realize that I would like to have commit A to introduce some
other_function() as well, so I add a fixup:

  ---A---B---f!A

with the following diff:

   int some_function(); 
  +int other_function();
   int another_function();

And then I often find that "rebase -i --autosquash" fails to apply
the commit B because it expects slightly different context around
the changed lines.

However, sometimes I see that if I do this:

  ---A---B
      \
       f!A

then "rebase --onto f!A A B" succeeds, nicely resolving the conflict
without bothering me. No idea why. I kinda hoped that you may know
this magic and incorporate it into "commit --onto" which will allow
to immediately get to the result of the rebase:

  ---A---f!A---B'

without spelling it all manually.

(And yeah, I'm actually Alexei, not Chris. That was my MUA being dumb
and using an old pseudonym than Google insists I'm called by.)