show: --ignore-missing

Instead of barfing, simply ignore bad object names seen in the
input. This is useful when reading from "git notes list" output
that may refer to objects that have already been garbage collected.

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

revision.h

@@ -36,7 +36,8 @@ struct rev_info {
 	const char *prefix;
 	const char *def;
 	struct pathspec prune_data;
-	unsigned int early_output;
+	unsigned int	early_output:1,
+			ignore_missing:1;
 
 	/* Traversal flags */
 	unsigned int	dense:1,