parse-options: add PARSE_OPT_LITERAL_ARGHELP for complicated argh's

Usually, the argh element in struct option points at a placeholder value
(e.g. "val"), and is shown in the usage message as

    --option=<val>

by enclosing the string inside of angle brackets.

When the option is more complex (e.g. optional arguments separated by a
comma), you would want to produce a usage message that looks like

    --option=<val1>[,<val2>]

In such a case, the caller can pass a string to argh with placeholders
already enclosed in necessary angle brackets (e.g.  "<val1>[,<val2>]")
and set this flag.
Signed-off-by: NStephen Boyd <bebarino@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

parse-options.c

@@ -361,6 +361,20 @@ int parse_options(int argc, const char **argv, const struct option *options,
 	return parse_options_end(&ctx);
 }
 
+static int usage_argh(const struct option *opts)
+{
+	const char *s;
+	int literal = opts->flags & PARSE_OPT_LITERAL_ARGHELP;
+	if (opts->flags & PARSE_OPT_OPTARG)
+		if (opts->long_name)
+			s = literal ? "[=%s]" : "[=<%s>]";
+		else
+			s = literal ? "[%s]" : "[<%s>]";
+	else
+		s = literal ? " %s" : " <%s>";
+	return fprintf(stderr, s, opts->argh);
+}
+
 #define USAGE_OPTS_WIDTH 24
 #define USAGE_GAP         2
 
@@ -421,15 +435,9 @@ int usage_with_options_internal(const char * const *usagestr,
 				break;
 			/* FALLTHROUGH */
 		case OPTION_STRING:
-			if (opts->argh) {
-				if (opts->flags & PARSE_OPT_OPTARG)
-					if (opts->long_name)
-						pos += fprintf(stderr, "[=<%s>]", opts->argh);
-					else
-						pos += fprintf(stderr, "[<%s>]", opts->argh);
-				else
-					pos += fprintf(stderr, " <%s>", opts->argh);
-			} else {
+			if (opts->argh)
+				pos += usage_argh(opts);
+			else {
 				if (opts->flags & PARSE_OPT_OPTARG)
 					if (opts->long_name)
 						pos += fprintf(stderr, "[=...]");

parse-options.h

@@ -31,6 +31,7 @@ enum parse_opt_option_flags {
 	PARSE_OPT_NONEG   = 4,
 	PARSE_OPT_HIDDEN  = 8,
 	PARSE_OPT_LASTARG_DEFAULT = 16,
+	PARSE_OPT_LITERAL_ARGHELP = 64,
 };
 
 struct option;
@@ -66,6 +67,9 @@ typedef int parse_opt_cb(const struct option *, const char *arg, int unset);
  *   PARSE_OPT_NONEG: says that this option cannot be negated
  *   PARSE_OPT_HIDDEN this option is skipped in the default usage, showed in
  *                    the long one.
+ *   PARSE_OPT_LITERAL_ARGHELP: says that argh shouldn't be enclosed in brackets
+ *				(i.e. '<argh>') in the help message.
+ *				Useful for options with multiple parameters.
  *
  * `callback`::
  *   pointer to the callback to use for OPTION_CALLBACK.