tag: use OPT_CMDMODE

This is just a demonstration of how the code would look like; I do
not think it is particularly easier to read than before myself.

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

builtin/tag.c

diff --git a/builtin/tag.c b/builtin/tag.c
index af3af3f..d8ae5aa 100644
--- a/builtin/tag.c
+++ b/builtin/tag.c
@@ -436,18 +436,18 @@
 	struct ref_lock *lock;
 	struct create_tag_options opt;
 	char *cleanup_arg = NULL;
-	int annotate = 0, force = 0, lines = -1, list = 0,
-		delete = 0, verify = 0;
+	int annotate = 0, force = 0, lines = -1;
+	int cmdmode = 0;
 	const char *msgfile = NULL, *keyid = NULL;
 	struct msg_arg msg = { 0, STRBUF_INIT };
 	struct commit_list *with_commit = NULL;
 	struct option options[] = {
-		OPT_BOOLEAN('l', "list", &list, N_("list tag names")),
+		OPT_CMDMODE('l', "list", &cmdmode, N_("list tag names"), 'l'),
 		{ OPTION_INTEGER, 'n', NULL, &lines, N_("n"),
 				N_("print <n> lines of each tag message"),
 				PARSE_OPT_OPTARG, NULL, 1 },
-		OPT_BOOLEAN('d', "delete", &delete, N_("delete tags")),
-		OPT_BOOLEAN('v', "verify", &verify, N_("verify tags")),
+		OPT_CMDMODE('d', "delete", &cmdmode, N_("delete tags"), 'd'),
+		OPT_CMDMODE('v', "verify", &cmdmode, N_("verify tags"), 'v'),
 
 		OPT_GROUP(N_("Tag creation options")),
 		OPT_BOOLEAN('a', "annotate", &annotate,
@@ -489,22 +489,19 @@
 	}
 	if (opt.sign)
 		annotate = 1;
-	if (argc == 0 && !(delete || verify))
-		list = 1;
+	if (argc == 0 && !cmdmode)
+		cmdmode = 'l';
 
-	if ((annotate || msg.given || msgfile || force) &&
-	    (list || delete || verify))
+	if ((annotate || msg.given || msgfile || force) && (cmdmode != 0))
 		usage_with_options(git_tag_usage, options);
 
-	if (list + delete + verify > 1)
-		usage_with_options(git_tag_usage, options);
 	finalize_colopts(&colopts, -1);
-	if (list && lines != -1) {
+	if (cmdmode == 'l' && lines != -1) {
 		if (explicitly_enable_column(colopts))
 			die(_("--column and -n are incompatible"));
 		colopts = 0;
 	}
-	if (list) {
+	if (cmdmode == 'l') {
 		int ret;
 		if (column_active(colopts)) {
 			struct column_options copts;
@@ -523,9 +520,9 @@
 		die(_("--contains option is only allowed with -l."));
 	if (points_at.nr)
 		die(_("--points-at option is only allowed with -l."));
-	if (delete)
+	if (cmdmode == 'd')
 		return for_each_tag_name(argv, delete_tag);
-	if (verify)
+	if (cmdmode == 'v')
 		return for_each_tag_name(argv, verify_tag);
 
 	if (msg.given || msgfile) {