If /bin/sh is /bin/dash, then the script will display an error if
$parent_sha1 is undefined. This patch works fixes the issue by
quoting both arguments to `test'. Arguments composed solely of
variable expansions should always be quoted, unless we know for
certain that the contents are defined.
Signed-off-by: Michael W. Olson <mwolson@gnu.org> Signed-off-by: Shawn O. Pearce <spearce@spearce.org>