http-fetch: correct --index-pack-arg documentation

The --packfile mode accepts one --index-pack-arg=<arg> option per
argument passed to index-pack, but its documentation and option
dependency errors still refer to the plural --index-pack-args form.

Correct the spelling and describe the repeatable per-argument form.

Signed-off-by: Ted Nyman <tnyman@openai.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: tnm-oai

Documentation/git-http-fetch.adoc

@@ -50,11 +50,11 @@ commit-id::
 	URL and uses index-pack to generate corresponding .idx and .keep files.
 	The hash is used to determine the name of the temporary file and is
 	arbitrary. The output of index-pack is printed to stdout. Requires
-	--index-pack-args.
+	one or more --index-pack-arg options.
 
---index-pack-args=<args>::
-	For internal use only. The command to run on the contents of the
-	downloaded pack. Arguments are URL-encoded separated by spaces.
+--index-pack-arg=<arg>::
+	For internal use only. An argument to the command run on the contents
+	of the downloaded pack. This option can be specified multiple times.
 
 --recover::
 	Verify that everything reachable from target is fetched.  Used after

http-fetch.c

@@ -155,7 +155,7 @@ int cmd_main(int argc, const char **argv)
 
 	if (packfile) {
 		if (!index_pack_args.nr)
-			die(_("the option '%s' requires '%s'"), "--packfile", "--index-pack-args");
+			die(_("the option '%s' requires '%s'"), "--packfile", "--index-pack-arg");
 
 		fetch_single_packfile(&packfile_hash, argv[arg],
 				      index_pack_args.v);
@@ -164,7 +164,7 @@ int cmd_main(int argc, const char **argv)
 	}
 
 	if (index_pack_args.nr)
-		die(_("the option '%s' requires '%s'"), "--index-pack-args", "--packfile");
+		die(_("the option '%s' requires '%s'"), "--index-pack-arg", "--packfile");
 
 	if (commits_on_stdin) {
 		commits = walker_targets_stdin(&commit_id, &write_ref);