How to avoid git rebase killing merge commits?

Question

Given the following git history:

    C-I    origin/master
   /
A-B-F-G-H  master
 \   /
  D-E      branch-b

I want to rebase my local master branch on top of origin/master, but I want to preserve the merge commit G. When I tried simply doing a git rebase origin/master while at master it squashed D..E as G and committed that with the commit message of E, so the history that there was a merge was lost. Is there some way of preserving this merge while still getting the rebase? For clarity, my intended result is:

A-B-C-I-F-G-H  master
 \       /
  D-----E      branch-b

score 67 · Accepted Answer · edited Nov 23 '19 at 07:14

67

Add --preserve-merges to your rebase command. In case there were conflict resolutions in your merge, add 'recursive theirs' strategy as a parameter as well.

EDIT: --preserve-merges is now deprecated, use --rebase-merges instead

edited Nov 23 '19 at 07:14

Lucien Dulac

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answered Jun 03 '11 at 01:07

Adam Dymitruk

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For absurd detail on what will happen with this flag, see also my answer at http://stackoverflow.com/questions/15915430/what-exactly-does-gits-rebase-preserve-merges-do-and-why. – Chris Sep 30 '13 at 20:03
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Can you elaborate why `recursive theirs` will help in this case? Merge commit `G` could have been created using a different conflict resolution strategy, could it not? – Nils_M Dec 10 '15 at 12:13

score 2 · Answer 2 · answered Jun 03 '11 at 00:07

This isn't going to be very pretty but I think you can do it.

Rebase F onto the origin/master as your new master branch:

git checkout F
git checkout -b new_master
git rebase origin/master

Merge branch-b into your new branch:

git merge branch-b

Cherry pick the remaining H commit onto your new master branch:

git cherry-pick master

Delete your old master branch:

git branch -D master

Unfortunately you will also have to do the merge again (hopefully it doesn't take any manual merging).

I didn't actually try this out, so I would make a backup of the repository first, but I am pretty confident that you will get what you want. I also suggest opening up gitk --all and refreshing the tree with "F5" after each command so you can see what is changing.

Someone else should still post if they know of a more elegant way to do it.

How to avoid git rebase killing merge commits?

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