Re: [PATCH v2 04/13] Teach rebase interactive the mark command

Johannes Schindelin [off-list ref] writes:

quoted

But instead you are thinking of letting me just say "X", and somehow 
make the machinery guess by noticing "Ah, original X is a merge between 
original A and B, and we have a merge between rewritten A and rewritten 
B, so we will treat that merge as rewritten "X"?

I actually was hoping we could avoid that, which feels messy.

...
But this got me thinking, and I think that to leave out the first parent 
was another mistake I made, so I really would like to have this syntax:

	merge <orig-commit> <parent1> <parent2>... <message>

This would allow to change the parents in the interactive rebase, and if 
<parent1> is not the current commit at that point, it would implicitly 
call "reset".

What appeals to me is the simplicity of this approach: you refer to the 
commits by calling them by their (original) name.

Ok, that clears my confusion, but it raises another issue.

In the context of "rebase -i", this may not be a problem, but by forcing
us to name commits always with original commits, we cannot build (instead
of rebuild) a history that does not yet exist using the sequencer
machinery, can we?

If we want to transplant "^C ^N O" in this history elsewhere:

      --o---C---N
               / 
          B---M
         /   /
        O---A

while inserting a new fix-up commit F on top of B before we merge that
side branch to rewritten A:

              --o---C---N'
                       / 
              B'--X---M'
             /       /
        O---Q-------A'

Would/Should the machinery somehow figure out that the merge between the
rewritten A (which is A') and an inserted commit X (which is made on top
of the rewritten B) corresponds to M in the original history?

This is not a made up example, but something I have to do once (on my
non-git days) or many more times (on my git days) every day when
rebuilding 'pu' on top of updated 'next' using updated tips of topic
branches.  I was hoping that the sequencer mechanism can help me
automating the process a bit more.