This is a problem with the repository configuration. You will have to diagnose it yourself.
I don't use Github for Mac I use Git from the command line.
Open up the Terminal.app and cd <the path of the first_app folder>
then do a git fetch origin
and see if that reviles anything works. You can also edit the first_app/.git/config
file and remove references to tracking branches in hopes Github for Mac recovers again.
You can also attempt to delete the first_app repo and then use Github for Mac to re clone it again.
As a side note, You might be better off not using Github for Mac and just use Git out of the box (on the command line) it takes a little bit more of a learning curve but worth it, and there is a much larger Git community then there is a Github for Mac community.
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