apt-mark help shows all commands now

cmdline/apt-mark.cc

@@ -386,6 +386,11 @@ bool ShowHelp(CommandLine &CmdL)
       "Commands:\n"
       "   auto - Mark the given packages as automatically installed\n"
       "   manual - Mark the given packages as manually installed\n"
+      "   hold - Mark a package as held back\n"
+      "   unhold - Unset a package set as held back\n"
+      "   showauto - Print the list of automatically installed packages\n"
+      "   showmanual - Print the list of manually installed packages\n"
+      "   showhold - Print the list of package on hold\n"
       "\n"
       "Options:\n"
       "  -h  This help text.\n"