[git] Couldn't push non-master branch to new repository

Repro:

1. Create new repo on keybase
2. Add as remote on existing local repo that doesn't have a master branch (default branch is develop, and almost no one checks out master on their PC)
3. With develop checked out, try `git push keybase develop`
4. git will show as if it succeeded.
5. On another PC, try to clone keybase git repo.
6. Run `ls -a` and see the folder is empty

Work around:

checking out master and pushing master first, then pushing develop etc. allows the data to be uploaded to keybase. Then cloning works and you can checkout develop and it will link to the remote keybase develop.

Perhaps this is spec for git... not too sure. Please close if so.

Start by reproducing the reported sequence: create a new Keybase repository, push only the develop branch, then clone it elsewhere and inspect the result. Determine whether the behavior is Git semantics or a Keybase remote issue; done means the supported behavior and any necessary change or documentation are clear.

Written by the indexing model from the issue text.