I was attempting to set the upstream branch on git and this happened:
$ git branch --set-upstream-to=origin/master warning: refname 'origin/master' is ambiguous. fatal: Ambiguous object name: 'origin/master'.
For some odd reason, I had a branch called "origin/master", so git wasn't sure if the upstream branch is another local branch or a remote branch.
$ git branch * master origin/master
In order to fix this, I deleted the local branch called "origin/master":
$ git branch -d "origin/master" Deleted branch origin/master (was e70042f). $ git branch * master
Then, I was able to set the upstream branch:
$ git branch --set-upstream-to=origin/master Branch master set up to track remote branch master from origin.