Conveniently, the places where we don't want this, and are
deliberately looking for dgit-self-made patches, are gdr-makepatches7
and mix-it in gdr-subcommands; there, we don't push, so don't end up
checking t-gdr-made-patches.
We also add this check to the appropriate place in gdr-subcommands.
Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>