git-blame: fix rev parameter handling.

We lacked "--" termination in the underlying init_revisions() call
which made it impossible to specify a revision that happens to
have the same name as an existing file.
Signed-off-by: NJunio C Hamano <junkio@cox.net>

builtin-blame.c

@@ -1787,6 +1787,7 @@ int cmd_blame(int argc, const char **argv, const char *prefix)
 	/* Now we got rev and path.  We do not want the path pruning
 	 * but we may want "bottom" processing.
 	 */
+	argv[unk++] = "--"; /* terminate the rev name */
 	argv[unk] = NULL;
 
 	init_revisions(&revs, NULL);