commit: remove full stop from usage help for -u

From api-parse-options.txt:

  `description` is a short string to describe the effect of the option.
  It shall begin with a lower-case letter and a full stop (`.`) shall be
  omitted at the end.

It also makes it less confusing if the argument is 'no.' or 'no'.

Signed-off-by: Stephen Boyd <bebarino@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/commit.c

@@ -147,7 +147,7 @@ static struct option builtin_commit_options[] = {
 		    "terminate entries with NUL"),
 	OPT_BOOLEAN(0, "amend", &amend, "amend previous commit"),
 	OPT_BOOLEAN(0, "no-post-rewrite", &no_post_rewrite, "bypass post-rewrite hook"),
-	{ OPTION_STRING, 'u', "untracked-files", &untracked_files_arg, "mode", "show untracked files, optional modes: all, normal, no. (Default: all)", PARSE_OPT_OPTARG, NULL, (intptr_t)"all" },
+	{ OPTION_STRING, 'u', "untracked-files", &untracked_files_arg, "mode", "show untracked files, optional modes: all, normal, no (Default: all)", PARSE_OPT_OPTARG, NULL, (intptr_t)"all" },
 	/* end commit contents options */
 
 	{ OPTION_BOOLEAN, 0, "allow-empty", &allow_empty, NULL,