rev-list: make it obvious that we do not support notes

The rev-list command does not have the internal
infrastructure to display notes. Running:

  git rev-list --notes HEAD

will silently ignore the "--notes" option. Running:

  git rev-list --notes --grep=. HEAD

will crash on an assert. Running:

  git rev-list --format=%N HEAD

will place a literal "%N" in the output (it does not even
expand to an empty string).

Let's have rev-list tell the user that it cannot fill the
user's request, rather than silently producing wrong data.
Likewise, let's remove mention of the notes options from the
rev-list documentation.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/rev-list.c

@@ -350,6 +350,9 @@ int cmd_rev_list(int argc, const char **argv, const char *prefix)
 	    revs.diff)
 		usage(rev_list_usage);
 
+	if (revs.show_notes)
+		die(_("rev-list does not support display of notes"));
+
 	save_commit_buffer = (revs.verbose_header ||
 			      revs.grep_filter.pattern_list ||
 			      revs.grep_filter.header_list);