Git rebase one branch on top of another branch

Question

In my git repo, I have a Master branch. One of the remote devs created a branch Branch1 and had a bunch of commits on it. I branched from Branch1

Answer 1

First backup your current Branch2:

# from Branch2
git checkout -b Branch2_backup

Then rebase Branch2 on Branch1:

# from Branch2
git fetch origin           # update all tracking branches, including Branch1
git rebase origin/Branch1  # rebase on latest Branch1

After the rebase your branch structure should look like this:

master --
         \
          1 -- 2 -- 3 -- 4 -- Branch2'

In the diagram above, the apostrophe on Branch2 indicates that every commit in the rebased Branch2 after commit 4 is actually a rewrite.

Keep in mind that you have now rewritten the history of Branch2 and if the branch is already published you will have to force push it to the remote via

git push --force origin Branch2

Force pushing can cause problems for anyone else using Branch2 so you should be careful when doing this.