[tui] help shortcut command raise list index out of range

# HG changeset patch
# User Takumi IINO <trot.thunder@gmail.com>
# Date 1339428758 -32400
# Node ID c35ef1706ac2b3788cb01641d7061de075146d87
# Parent  ebdaabf52b73e635d2c9348005e4529c2218d041
[tui] help shortcut command raise list index out of range

Input ":?[enter]" into footer prompt, raise IndexError: list index out of range.

Traceback (most recent call last):
  File "/usr/bin/hgview", line 33, in <module>
    main()
  File "/usr/lib/python2.6/site-packages/hgviewlib/application.py", line 192, in main
    sys.exit(start(repo, opts, args, parser.error))
  File "/usr/lib/python2.6/site-packages/hgviewlib/application.py", line 143, in start
    return app.exec_()
  File "/usr/lib/python2.6/site-packages/hgviewlib/curses/application.py", line 87, in exec_
    out = self.mainloop.run()
  File "/usr/lib/python2.6/site-packages/urwid/main_loop.py", line 274, in run
    self.screen.run_wrapper(self._run)
  File "/usr/lib/python2.6/site-packages/urwid/raw_display.py", line 237, in run_wrapper
    return fn()
  File "/usr/lib/python2.6/site-packages/urwid/main_loop.py", line 307, in _run
    self.event_loop.run()
  File "/usr/lib/python2.6/site-packages/urwid/main_loop.py", line 682, in run
    self._loop()
  File "/usr/lib/python2.6/site-packages/urwid/main_loop.py", line 720, in _loop
    self._watch_files[fd]()
  File "/usr/lib/python2.6/site-packages/urwid/main_loop.py", line 358, in _update
    self.process_input(keys)
  File "/usr/lib/python2.6/site-packages/urwid/main_loop.py", line 447, in process_input
    k = self._topmost_widget.keypress(self.screen_size, k)
  File "/usr/lib/python2.6/site-packages/hgviewlib/curses/mainframe.py", line 141, in keypress
    key = super(MainFrame, self).keypress(size, key)
  File "/usr/lib/python2.6/site-packages/urwid/container.py", line 629, in keypress
    return self.footer.keypress((maxcol,),key)
  File "/usr/lib/python2.6/site-packages/hgviewlib/curses/mainframe.py", line 204, in keypress
    cmdline = self.call_command()
  File "/usr/lib/python2.6/site-packages/hgviewlib/curses/mainframe.py", line 273, in call_command
    cmdline = 'help %s' % cmdline[:-1].split(None, 1)[0]
IndexError: list index out of range

diff --git a/hgviewlib/curses/mainframe.py b/hgviewlib/curses/mainframe.py
--- a/hgviewlib/curses/mainframe.py
+++ b/hgviewlib/curses/mainframe.py
@@ -269,7 +269,9 @@
             self.footer.set('default', '', '')
             return
         cmdline = cmdline.strip()
-        if cmdline.endswith('?'):
+        if cmdline == '?':
+            cmdline = 'help'
+        elif cmdline.endswith('?'):
             cmdline = 'help %s' % cmdline[:-1].split(None, 1)[0]
         elif cmdline.startswith('?'):
             cmdline = 'help %s' % cmdline[1:].split(None, 1)[0]