i18n: help: mark strings for translation

This patch also marks most common commands' synopsis for translation
so that "git help" gives a friendly listing.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/git.c b/git.c
index 3805616..4486deb 100644
--- a/git.c
+++ b/git.c
@@ -13,7 +13,7 @@
 	"           <command> [<args>]";
 
 const char git_more_info_string[] =
-	"See 'git help <command>' for more information on a specific command.";
+	N_("See 'git help <command>' for more information on a specific command.");
 
 static struct startup_info git_startup_info;
 static int use_pager = -1;