[orca] Mark two additional argparse strings for translation

[Joanmarie Diggs <joanied src gnome org>]

commit cfeb9a1754b3fdd6cd9a0c875fdb5ea191dfc5a0
Author: Joanmarie Diggs <jdiggs igalia com>
Date:   Fri Jun 26 13:45:12 2015 -0400

    Mark two additional argparse strings for translation

 src/orca/messages.py    |    9 +++++++++
 src/orca/orca_bin.py.in |    8 ++++++--
 2 files changed, 15 insertions(+), 2 deletions(-)
---
diff --git a/src/orca/messages.py b/src/orca/messages.py
index 328ae77..0aceebf 100644
--- a/src/orca/messages.py
+++ b/src/orca/messages.py
@@ -192,6 +192,15 @@ CLI_ENABLE_OPTION = _("Force use of option")
 # using the '-e, --enable' or '-d, --disable' command line options.
 CLI_OPTION = _("OPTION")
 
+# Translators: This string appears when using 'Orca -h' at the command line.
+# It serves as a sort of title and is followed by a detailed list of Orca's
+# optional command-line arguments.
+CLI_OPTIONAL_ARGUMENTS = _("Optional arguments")
+
+# Translators: This string appears when using 'Orca -h' at the command line.
+# It is followed by a brief list of Orca's optional command-line arguments.
+CLI_USAGE = _("Usage: ")
+
 # Translators: This message is displayed when the user starts Orca from the
 # command line and includes an invalid option or argument. After the message,
 # the list of invalid items, as typed by the user, is displayed.
diff --git a/src/orca/orca_bin.py.in b/src/orca/orca_bin.py.in
index 2991f4b..f8c86f9 100644
--- a/src/orca/orca_bin.py.in
+++ b/src/orca/orca_bin.py.in
@@ -81,8 +81,10 @@ class HelpFormatter(argparse.HelpFormatter):
     def __init__(self, prog, indent_increment=2, max_help_position=32,
                  width=None):
 
-        super(HelpFormatter, self).__init__(
-            prog, indent_increment, max_help_position, width)
+        super().__init__(prog, indent_increment, max_help_position, width)
+
+    def add_usage(self, usage, actions, groups, prefix=None):
+        super().add_usage(usage, actions, groups, messages.CLI_USAGE)
 
 class Parser(argparse.ArgumentParser):
     def __init__(self, *args, **kwargs):
@@ -119,6 +121,8 @@ class Parser(argparse.ArgumentParser):
         self.add_argument(
             "--debug", action="store_true", help=messages.CLI_ENABLE_DEBUG)
 
+        self._optionals.title = messages.CLI_OPTIONAL_ARGUMENTS
+
     def parse_known_args(self, *args, **kwargs):
         opts, invalid = super(Parser, self).parse_known_args(*args, **kwargs)
         try: