Merge branch 'gc/zero-length-branch-config-fix'

A misconfigured 'branch..remote' led to a bug in configuration
parsing.

* gc/zero-length-branch-config-fix:
  remote.c: reject 0-length branch names
  remote.c: don't BUG() on 0-length branch names

diff --cc remote.c
Simple merge

diff --cc t/t5516-fetch-push.sh
Simple merge