The builtin-fetch topic changed push's handling of --all to setting
the new TRANSPORT_PUSH_ALL flag before starting the push subroutine
for the given transport. Unfortunately not all references within
builtin-push were changed to test this flag therefore allowing push
to incorrectly accept refspecs and --all.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>