Rebase without removing old branch

Question

I have the following situation in Git:

A--B--C--D--E--F--G
       \--H--I

I want to rebase the branch, but keep the original branch. So I want this:

A--B--C--D--E--F--G
       \--H--I     \--H'--I'

The reason is that it's possible that my rebased branch will break things. If it does too much, and I can't easily fix it, I want to keep working with the old branch.

This is in a situation where the master branch is actually based on another repository and is a long way behind the original repository. I'm trying to get our (H-I) branch back up to the latest version of the original master branch.

Answer 1

Just create a new branch an work on it.

git checkout your-old-branch
git checkout -b to-be-rebased
git rebase master

and work on to-be-rebased until you have something workable.

So your-old-branch still points to the same exact commit, unaffected.

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...and the two first checkout steps can be combined into one (as pointed out by Johnathon) to avoid an unnecessary check out step :

git checkout -b to-be-rebased your-old-branch

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Lastly, to be fair to Lasse's comment, it's true that we could have proceeded with cherry-pick to the same effect :

git checkout -b new-branch master
git cherry-pick master..your-old-branch