Rebase only part of a branch

Question

I've got two branches (and master). Branch 2 is based on Branch 1 is based on master. I've submitted Branch 1 for review, it had some changes, I rebased some of those changes into history and merged the result into master.

Now I need to rebase Branch 2 on top of master to prepare it for review/merge.

The problem is that Branch 2 still contains the original commits of Branch 1, which don't exist anymore, so git gets confused. I tried rebase -i to drop the original commits of Branch 1, but the commits of Branch 2 don't base on top of master-before-branch-1.

What I need to do is take branch 2, drop some commits, and rebase just the remaining commits on top of master in a single operation. But I only know how to do these two operations in two distinct steps.

How can I rebase part of my branch onto another branch, dropping all commits that are not in common ancestry, except the ones I specify (e.g. from HEAD~2 up)?

Here's the current state:

master                     new branch 1 - - - - - - - - - - - | - - - - - - - - -     \      \   branch 1       \ _ _ _ _ _ _ _                      \                       \     branch 2                        \ _ _ _ _ _ _ _ 

What I want to end up with:

master            new branch 1     - - - - - - - | - - - - - - - - - -                                    \                                     \                                      \                                       \    branch 2                                        - - - - - - - - -  

Answer 1

The actual command would be:

git rebase --onto newbranch1 branch1 branch2 

That will replay on top of new_branch1 all commits after branch1 up to branch2 HEAD.

As Joshua Goldberg puts it in the comments:

 git rebase --onto <place-to-put-it> <last-change-that-should-NOT-move> <change to move> 

As Denis Sivtsov illustrates in the comments:

If you need only replay the last commit only from branch, in this case work:

git rebase --onto newbranch1 HEAD~1