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, creating a new branch called Branch2 (git checkout -b Branch2 Branch1) such that Branch2 head was on the last commit added to Branch1:(Looks like this)

Master---          \           Branch1--commit1--commit2                                    \                                     Branch2 (my local branch)  

Branch1 has had a number of changes. The other dev squashed his commits and then added a few more commits. Meanwhile, ive had a bunch of changes in my branch but havent committed anything yet. Current structure looks like this:

  Master---              \              Branch1--squashed commit1,2--commit3--commit4                                        \                                         Branch2 (my local branch) 

Now I want have to rebase my changes on top of Branch1. I am supremely confused on how to go about this. I know the 1st step will be to commit my changes using git add . and git commit -m "message". But do i then push? using git push origin Branch2 ? or git push origin Branch2 Branch1 ? Help is much needed and GREATLY appreciated, also if I can some how create a backup of my branch, it will be great in case I screw something up

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.

Answer 2

git rebase branch1 branch2 will rebase branch branch2 onto branch1. Operationally, this means any commits which are contained only in branch2 (and not in branch1) will be replayed on top of branch1, moving the branch2 pointer with them. See git rebase --help for more information, including diagrams of this operation.

The operation might produce some conflicts which then you'll have to resolve manually. Edit the affected files, merging content and removing any failed hunks. Afterwards, mark the files as merged using git add <file> and then continue the rebase using git rebase --continue. Repeat until it is done.

Once done, you have nothing else to do. You don't have to push. However if you wish to mirror your new changes to some other repository (for instance, to share it with others or to have those changes in another repository of yours), do a final git push.