Preserve merge changes with rebase -p

Preserve merge changes with rebase -p

[Matteo Cypriani]

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Hi all,

I needed to change the author of a commit that was before a merge in the 
history. Here is a figure of my situation, E being the commit I want to edit, 
and M the problematic merge commit:

     o---o---o---o---o---o---o---o  master
              \       \ 
               o---E---M---o---o  topic


In a simple case, git rebase -i -p from topic does the trick here, I can amend 
E and M is re-created correctly.

The thing is, my M was not a "simple merge commit", but contained some changes 
needed for the code in master and topic to work together. In that case, git 
rebase -i -p recreates a merge commit, but it does not keep the changes 
introduced in M.

Is there any way to keep the M's changes in my case (except to manually patch 
& amend the re-created merge commit) ?
If not, maybe it would be a nice functionnality to implement ?

Cheers,
  Matteo

P.S.: Please CC me if you answer to this e-mail, as I'm not subscribed to the 
list.

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Re: Preserve merge changes with rebase -p

[Andrew Wong]

On 06/21/2011 08:11 AM, Matteo Cypriani wrote:
> The thing is, my M was not a "simple merge commit", but contained some changes 
> needed for the code in master and topic to work together. In that case, git 
> rebase -i -p recreates a merge commit, but it does not keep the changes 
> introduced in M.
>
> Is there any way to keep the M's changes in my case (except to manually patch 
> & amend the re-created merge commit) ?
>   
Unfortunately, I don't think there's any nice way to do it right now. I
think what you could do for now is make the "pick <M>" into a "edit
<M>", together with other changes you want to make. And then when you
get to "edit M", do a "git cherry-pick -n -m 1 <M>", or "-m 2" depending
on how your merge was done. That should bring your changes over. Then
you just need resolve and add any conflicts, and do a "rebase --continue".

I've only tried it on a simple case and that seems to work.

> If not, maybe it would be a nice functionnality to implement ?
>   
I imagine this is pretty useful feature to have too. I could look into
adding this support when I got a chance. I haven't given it much thought
yet though, so I don't know how feasible it is.

Re: Preserve merge changes with rebase -p

[Matteo Cypriani]

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Le mardi 21 juin 2011 16:44:48, Andrew Wong a écrit :
> Unfortunately, I don't think there's any nice way to do it right now. I
> think what you could do for now is make the "pick <M>" into a "edit
> <M>", together with other changes you want to make. And then when you
> get to "edit M", do a "git cherry-pick -n -m 1 <M>", or "-m 2" depending
> on how your merge was done. That should bring your changes over. Then
> you just need resolve and add any conflicts, and do a "rebase --continue".

Thank you, I'll try that the next time.


> I imagine this is pretty useful feature to have too. I could look into
> adding this support when I got a chance.

That would be great, many thanks in advance!

Cheers,

  Matteo

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