git rebase fatal: Needed a single revision

You need to provide the name of a branch (or other commit identifier), not the name of a remote to git rebase.

E.g.:

git rebase origin/master

not:

git rebase origin

Note, although origin should resolve to the the ref origin/HEAD when used as an argument where a commit reference is required, it seems that not every repository gains such a reference so it may not (and in your case doesn't) work. It pays to be explicit.

Check that you spelled the branch name correctly. I was rebasing a story branch (i.e. branch_name) and forgot the story part. (i.e. story/branch_name) and then git spit this error at me which didn't make much sense in this context.