If you have not committed:
git stash
git checkout some-branch
git stash pop
? If you have committed and have not changed anything since:
git log --oneline -n1 # this will give you the SHA
git checkout some-branch
git merge ${commit-sha}
If you have committed and then done extra work:
git stash
git log --oneline -n1 # this will give you the SHA
git checkout some-branch
git merge ${commit-sha}
git stash pop