Files in $HOME/.local/share/dbus-1/services/ do not override those in /usr/share/dbus-1/services/

This breaks the XDG Base Directory Specification [1] which clearly states

"The base directory defined by $XDG_DATA_HOME is considered more important than any of the base directories defined by $XDG_DATA_DIRS. The base directory defined by $XDG_CONFIG_HOME is considered more important than any of the base directories defined by $XDG_CONFIG_DIRS."

This is a very serious issue that prevents the user from overriding misguided system-wide configuration. Both the 1.2 and 1.4 branches suffer from this.

The bug is quite plain in dbus/dbus-sysdeps-unix.c, line 3502:

  xdg_data_home = _dbus_getenv ("XDG_DATA_HOME");
  xdg_data_dirs = _dbus_getenv ("XDG_DATA_DIRS");

  if (xdg_data_dirs != NULL)
    {
      if (!_dbus_string_append (&servicedir_path, xdg_data_dirs))
        goto oom;

      if (!_dbus_string_append (&servicedir_path, ":"))
        goto oom;
    }
  else
    {
      if (!_dbus_string_append (&servicedir_path, "/usr/local/share:/usr/share:"))
        goto oom;
    }

  /*
   * add configured datadir to defaults
   * this may be the same as an xdg dir
   * however the config parser should take
   * care of duplicates
   */
  if (!_dbus_string_append (&servicedir_path, DBUS_DATADIR":"))
        goto oom;

  if (xdg_data_home != NULL)
    {
      if (!_dbus_string_append (&servicedir_path, xdg_data_home))
        goto oom;
    }


i.e. XDG_DATA_HOME is used AFTER XDG_DATA_DIRS

[1] http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html