builtin/shortlog.c: make usage string consistent with log

"--" is used to separate pathspecs from the rev specs, and not rev
specs from the options, as the shortlog_usage string currently
indicates.  In correcting this usage string, make it consistent with
the log_usage string.

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/shortlog.c

@@ -10,9 +10,7 @@
 #include "parse-options.h"
 
 static char const * const shortlog_usage[] = {
-	N_("git shortlog [-n] [-s] [-e] [-w] [rev-opts] [--] [<commit-id>... ]"),
-	"",
-	N_("[rev-opts] are documented in git-rev-list(1)"),
+	N_("git shortlog [<options>] [<revision range>] [[--] [<path>...]]"),
 	NULL
 };