How to undo a merge on Bitbucket?

Question

You need to first clone the repository on your local system (you can get the repo URL in SSH or HTTPS format from the "Overview" page of the repository in Bitbucket):

git clone [email protected]:my/repo.git
-or-
git clone https://[email protected]/my/repo.git

git checkout master

.. then revert the most recent commit. First list the available commits with:

git log

.. then select the commit before the merge:

git reset --hard 72ead1c4c1778c23c277c4f15bbb68f3bb205f54

.. where the hash is the hash of the commit before the merge (from the log). Finally, force-push the changes back to Bitbucket, overwriting history.

git push -f

Naturally if the repo is shared, and its other users have pulled your most recent commit and built atop it, they won't be happy. So in that case be sure to notify everybody of what you're doing.

revert, as mentioned in the other answers is another option; it keeps the commit you made, but modifies the repository further (with a new commit) in such way that it undoes the changes you made. Whether you want to use revert depends on whether you want the information in your commit to remain in the repo history or not.

For more detail on undoing changes in git, see a good tutorial page by Atlassian.

A "Revert pull request" feature was implemented in Bitbucket in 2017.

To revert a pull request:

1. From the pull request, click the Revert button in the top right. (Optional) From the Revert pull request dialog, change the Branch name for the new branch you're about to create.
2. Click the Revert button. Once you click Revert, Bitbucket creates the new branch. Even if you cancel the pull request, the revert branch remains in the repository.
3. The Create a pull request page opens with the revert branch as the source. After you add your reviewers and make additional changes, click Create.

Source: the docs.

I would suggest doing a revert instead, since you are reverting a public repo.

git revert HEAD
git push -f origin

to undo the changes of a commit: git revert <commit id>

First, on your local machine, on the branch you merged into (e.g. master):

git revert -m 1 HEAD

or:

git revert -m 1 <merge commit hash>

Then push to origin.

Alternatively, if you cannot push directly to master, create a new branch off of master first before reverting, then push and create a new PR with this new branch against master and merge on bitbucket.