Make "git-log --" without paths behave the same as "git-log" without --

"git log" family of commands, even when run from a subdirectory,
do not limit the revision range with the current directory as
the path limiter, but with double-dash without any paths after
it, i.e. "git log --" do so.  It was a mistake to have a
difference between "git log --" and "git log" introduced in
commit ae56354 (First cut at
libifying revlist generation).

Signed-off-by: Junio C Hamano <gitster@pobox.com>

revision.c

@@ -896,7 +896,8 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs, const ch
 			continue;
 		argv[i] = NULL;
 		argc = i;
-		revs->prune_data = get_pathspec(revs->prefix, argv + i + 1);
+		if (argv[i + 1])
+			revs->prune_data = get_pathspec(revs->prefix, argv + i + 1);
 		seen_dashdash = 1;
 		break;
 	}