Set debianBranch in execMake(), use it in createGitRepository()
Set debianBranch in execMake(), use it in createGitRepository()

This minor refactoring prepares the code for the next commit, where we
will need to know the Debian branch in `execMake()`.

anthonyfok/dh-make-golang,anthonyfok/dh-make-golang,Debian/dh-make-golang,Debian/dh-make-golang