checkout-index: improve argument help for --stage

Spell out all alternatives and avoid using a numerical range operator,
as it is not mentioned in CodingGuidelines and the resulting string is
still concise.  Wrap them in parentheses to document clearly that the
"--stage=" part is common among them.

Signed-off-by: Rene Scharfe <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: rscharfe

builtin/checkout-index.c

@@ -172,7 +172,7 @@ int cmd_checkout_index(int argc, const char **argv, const char *prefix)
 			N_("write the content to temporary files")),
 		OPT_STRING(0, "prefix", &state.base_dir, N_("string"),
 			N_("when creating files, prepend <string>")),
-		{ OPTION_CALLBACK, 0, "stage", NULL, "1-3|all",
+		{ OPTION_CALLBACK, 0, "stage", NULL, "(1|2|3|all)",
 			N_("copy out the files from named stage"),
 			PARSE_OPT_NONEG, option_parse_stage },
 		OPT_END()