builtin/checkout: reword hint for -b

Shift the 'new' from the param to the hint, and expand the hint.

Signed-off-by: Tay Ray Chuan <rctay89@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/checkout.c

@@ -657,7 +657,8 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 	int dwim_new_local_branch = 1;
 	struct option options[] = {
 		OPT__QUIET(&opts.quiet),
-		OPT_STRING('b', NULL, &opts.new_branch, "new branch", "branch"),
+		OPT_STRING('b', NULL, &opts.new_branch, "branch",
+			   "create and checkout a new branch"),
 		OPT_BOOLEAN('l', NULL, &opts.new_branch_log, "log for new branch"),
 		OPT_SET_INT('t', "track",  &opts.track, "track",
 			BRANCH_TRACK_EXPLICIT),