How to fix committing to the wrong Git branch?

If you haven't yet pushed your changes, you can also do a soft reset:

git reset --soft HEAD^

This will revert the commit, but put the committed changes back into your index. Assuming the branches are relatively up-to-date with regard to each other, git will let you do a checkout into the other branch, whereupon you can simply commit:

git checkout branch
git commit -c ORIG_HEAD

The -c ORIG_HEAD part is useful to not type commit message again.

4 years late on the topic, but this might be helpful to someone.

If you forgot to create a new branch before committing and committed all on master, no matter how many commits you did, the following approach is easier:

git stash                       # skip if all changes are committed
git branch my_feature
git reset --hard origin/master
git checkout my_feature
git stash pop                   # skip if all changes were committed

Now you have your master branch equals to origin/master and all new commits are on my_feature. Note that my_feature is a local branch, not a remote one.

If you have a clean (un-modified) working copy

To rollback one commit (make sure you note the commit's hash for the next step):

git reset --hard HEAD^

To pull that commit into a different branch:

git checkout other-branch
git cherry-pick COMMIT-HASH

If you have modified or untracked changes

Also note that git reset --hard will kill any untracked and modified changes you might have, so if you have those you might prefer:

git reset HEAD^
git checkout .