How to avoid git rebase killing merge commits?

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.

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