parse-options: teach "git cmd -h" to show alias as alias

There is a long-standing NEEDSWORK comment that complains about
inconsistency between how an aliased option ("git clone --recurse"
which is the only one that currently exists) gives a help text in
a usage-error message vs "git cmd -h").  Get rid of it and then
make sure we say an option is an alias for another, instead of
repeating the same short help text for both, which leads to "they
seem to do the same---is there any subtle difference?" puzzlement
to end-users.

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

parse-options.c

@@ -648,6 +648,7 @@ static struct option *preprocess_options(struct parse_opt_ctx_t *ctx,
 		int short_name;
 		const char *long_name;
 		const char *source;
+		struct strbuf help = STRBUF_INIT;
 		int j;
 
 		if (newopt[i].type != OPTION_ALIAS)
@@ -659,6 +660,7 @@ static struct option *preprocess_options(struct parse_opt_ctx_t *ctx,
 
 		if (!long_name)
 			BUG("An alias must have long option name");
+		strbuf_addf(&help, _("alias of --%s"), source);
 
 		for (j = 0; j < nr; j++) {
 			const char *name = options[j].long_name;
@@ -669,15 +671,10 @@ static struct option *preprocess_options(struct parse_opt_ctx_t *ctx,
 			if (options[j].type == OPTION_ALIAS)
 				BUG("No please. Nested aliases are not supported.");
 
-			/*
-			 * NEEDSWORK: this is a bit inconsistent because
-			 * usage_with_options() on the original options[] will print
-			 * help string as "alias of %s" but "git cmd -h" will
-			 * print the original help string.
-			 */
 			memcpy(newopt + i, options + j, sizeof(*newopt));
 			newopt[i].short_name = short_name;
 			newopt[i].long_name = long_name;
+			newopt[i].help = strbuf_detach(&help, NULL);
 			break;
 		}
 

t/t0040-parse-options.sh

@@ -54,7 +54,7 @@ Alias
     -A, --alias-source <string>
                           get a string
     -Z, --alias-target <string>
-                          get a string
+                          alias of --alias-source
 
 EOF