diff: parse separate options --stat-width n, --stat-name-width n

Part of a campaign for unstuck forms of options.

[jn: with some refactoring]

Signed-off-by: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff.c

@@ -3035,16 +3035,34 @@ static int stat_opt(struct diff_options *options, const char **av)
 	char *end;
 	int width = options->stat_width;
 	int name_width = options->stat_name_width;
+	int argcount = 1;
 
 	arg += strlen("--stat");
 	end = (char *)arg;
 
 	switch (*arg) {
 	case '-':
-		if (!prefixcmp(arg, "-width="))
-			width = strtoul(arg + 7, &end, 10);
-		else if (!prefixcmp(arg, "-name-width="))
-			name_width = strtoul(arg + 12, &end, 10);
+		if (!prefixcmp(arg, "-width")) {
+			arg += strlen("-width");
+			if (*arg == '=')
+				width = strtoul(arg + 1, &end, 10);
+			else if (!*arg && !av[1])
+				die("Option '--stat-width' requires a value");
+			else if (!*arg) {
+				width = strtoul(av[1], &end, 10);
+				argcount = 2;
+			}
+		} else if (!prefixcmp(arg, "-name-width")) {
+			arg += strlen("-name-width");
+			if (*arg == '=')
+				name_width = strtoul(arg + 1, &end, 10);
+			else if (!*arg && !av[1])
+				die("Option '--stat-name-width' requires a value");
+			else if (!*arg) {
+				name_width = strtoul(av[1], &end, 10);
+				argcount = 2;
+			}
+		}
 		break;
 	case '=':
 		width = strtoul(arg+1, &end, 10);
@@ -3058,7 +3076,7 @@ static int stat_opt(struct diff_options *options, const char **av)
 	options->output_format |= DIFF_FORMAT_DIFFSTAT;
 	options->stat_name_width = name_width;
 	options->stat_width = width;
-	return 1;
+	return argcount;
 }
 
 int diff_opt_parse(struct diff_options *options, const char **av, int ac)