I have a remote bare repository hub. I work only in the master branch.
The last sentence of this error message below makes me wonder: How do I find
For the sake of completeness: the previous answers tell how to set the upstream branch, but not how to see it.
There are a few ways to do this:
git branch -vv shows that info for all branches. (formatted in blue in most terminals)
cat .git/config shows this also.
For reference: