Make GIT-VERSION-GEN tolerate missing git describe command
I think it is probably a bug that "git non_existent_command"
returns its error message to stdout without an error, where
"git-non_existent_command" behaves differently and does return an
error.
Older versions of git did not implement "git describe" and
GIT-VERSION-GEN produces an empty version string if run on
a system with such a git installed. The consequence
is that "make rpm" fails.
This patch fixes GIT-VERSION-GEN so that it works in the
absence of a working "git describe"
Signed-off-by: John Ellson <ellson@research.att.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>