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MeanwhileInHell
MeanwhileInHell

Reputation: 7053

Rebasing branch1 with changes in master from branch2

I have two branches off master; branch1 and branch2. I have some changes made on branch1 and have an active PR up for this. I also have changes on branch2 that have been reviewed and merged into master and the branch subsequently deleted.

I have updated my local master by doing a git fetch -ap and a git pull which brought down the changes made in branch2. I now want to update branch1 with these changes so that the only differences are the ones I have made on that branch. I tried git checkout branch1 followed by git rebase master.

However, when I do a git status on branch1 it says:

On branch branch1
Your branch and 'origin/branch1' have diverged,
and have 3 and 1 different commits each, respectively.
  (use "git pull" to merge the remote branch into yours)

Doing a git pull here opens up a merge comment dialog. But now when I look at my PR on branch1 it now includes the changes from branch2 as new changes. What has happened here, and how can I fix this?

Upvotes: 0

Views: 159

Answers (1)

Scott Weldon
Scott Weldon

Reputation: 10217

(For this answer, I'm assuming you have branch1 checked out. If not, do git checkout branch1.)

When you do git rebase master, you are rewriting the commits in branch1, since they now have a new parent. This is what your history might look like:

X--*--Y [master]
 \     \
  \     A'--B'--C' [branch1]  <--
   \                            | (git rebase master)
    A--B--C [origin/branch1] ----

where e.g. A' has the same contents as A, but a different commit hash, because its parent is Y instead of X.

Since the commits have changed, you will have to force-update origin. After you finish the rebase, you should do:

git push --force-with-lease

However, since you already did a git pull post-rebase, you'll need to fix that first. Do e.g.:

git reset --hard C'

Or:

git reset --hard HEAD^

This will remove the merge commit from branch1, and you can force push as described above. First, to ensure your branch was reset properly, do:

git log --oneline --decorate master..HEAD

The output of that command should show all the commits that should be in branch1, and only those commits.

(Aside: if you do git status at this point, you might see some output like this:

On branch branch1
Your branch is behind 'origin/branch1' by 2 commits, and can be fast-forwarded.
  (use "git pull" to update your local branch)

You can safely ignore this warning, since the one of those commits was the merge commit, and the other was the 1 different commit from your original error message.)

As mentioned above, at this point you should do:

git push --force-with-lease

And now the remote branch1 will have the same commits as your local branch1.

Obligatory warning: Since a rebase rewrites history, this can be dangerous / disruptive for anyone else working on this branch. Be sure you clearly communicate what you have done with anyone you are collaborating with.

Upvotes: 1

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