builtin-am: implement legacy -b/--binary option

The -b/--binary option was initially implemented in 087b6742 (git-am:
--binary; document --resume and --binary., 2005-11-16). The option will
pass the --binary flag to git-apply to allow it to apply binary patches.

However, in 2b6eef94 (Make apply --binary a no-op., 2006-09-06), --binary
was been made a no-op in git-apply. Following that, since cb3a160d
(git-am: ignore --binary option, 2008-08-09), the --binary option in
git-am is ignored as well.

In 6c15a1c6 (am: officially deprecate -b/--binary option, 2012-03-13),
the --binary option was tweaked to its present behavior: when set, the
message:

	The -b/--binary option has been a no-op for long time, and it
	will be removed. Please do not use it anymore.

will be printed.

Re-implement this in builtin/am.c.
Signed-off-by: NPaul Tan <pyokagan@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

builtin/am.c

@@ -2126,6 +2126,7 @@ enum resume_mode {
 int cmd_am(int argc, const char **argv, const char *prefix)
 {
 	struct am_state state;
+	int binary = -1;
 	int keep_cr = -1;
 	int patch_format = PATCH_FORMAT_UNKNOWN;
 	enum resume_mode resume = RESUME_FALSE;
@@ -2139,6 +2140,8 @@ int cmd_am(int argc, const char **argv, const char *prefix)
 	struct option options[] = {
 		OPT_BOOL('i', "interactive", &state.interactive,
 			N_("run interactively")),
+		OPT_HIDDEN_BOOL('b', "binary", &binary,
+			N_("(historical option -- no-op")),
 		OPT_BOOL('3', "3way", &state.threeway,
 			N_("allow fall back on 3way merging if needed")),
 		OPT__QUIET(&state.quiet, N_("be quiet")),
@@ -2239,6 +2242,10 @@ int cmd_am(int argc, const char **argv, const char *prefix)
 
 	argc = parse_options(argc, argv, prefix, options, usage, 0);
 
+	if (binary >= 0)
+		fprintf_ln(stderr, _("The -b/--binary option has been a no-op for long time, and\n"
+				"it will be removed. Please do not use it anymore."));
+
 	if (read_index_preload(&the_index, NULL) < 0)
 		die(_("failed to read the index"));