tag: Check that options are only allowed in the appropriate mode

If "git tag -d -l -v ..." is called, only "-l" is honored, which is
arbitrary and wrong. Also, unrecognized options are accepted in the
wrong modes, causing for example "git tag -n 100" to create a tag
named "100" while the user may have wanted to type "git tag -n100".

This patch checks that "git tag" knows in what mode it operates before
performing any operation and accepts only the related options.

Signed-off-by: Samuel Tardieu <sam@rfc1149.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-tag.c

@@ -344,7 +344,7 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
 	const char *object_ref, *tag;
 	struct ref_lock *lock;
 
-	int annotate = 0, sign = 0, force = 0, lines = 0,
+	int annotate = 0, sign = 0, force = 0, lines = -1,
 		list = 0, delete = 0, verify = 0;
 	const char *msgfile = NULL, *keyid = NULL;
 	struct msg_arg msg = { 0, STRBUF_INIT };
@@ -380,9 +380,19 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
 	}
 	if (sign)
 		annotate = 1;
+	if (argc == 0 && !(delete || verify))
+		list = 1;
 
+	if ((annotate || msg.given || msgfile || force) &&
+	    (list || delete || verify))
+		usage_with_options(git_tag_usage, options);
+
+	if (list + delete + verify > 1)
+		usage_with_options(git_tag_usage, options);
 	if (list)
-		return list_tags(argv[0], lines);
+		return list_tags(argv[0], lines == -1 ? 0 : lines);
+	if (lines != -1)
+		die("-n option is only allowed with -l.");
 	if (delete)
 		return for_each_tag_name(argv, delete_tag);
 	if (verify)
@@ -407,11 +417,6 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
 		}
 	}
 
-	if (argc == 0) {
-		if (annotate)
-			usage_with_options(git_tag_usage, options);
-		return list_tags(NULL, lines);
-	}
 	tag = argv[0];
 
 	object_ref = argc == 2 ? argv[1] : "HEAD";