With 0.124 version:
Connect a joystick on the USB port (Tried with a Sony DualShock 3).
Run a game, check that joystick is working (Button 1 is 'SELECT' by default, instead of 'X'). Check that joystick is working.
Go to Input (general), Player 1 Controls, Choose P1 Button 1
Press a joystick button : nothing happens :
Expected behaviour : assign last joystick button pressed to P1 Button 1
Note that you cannot reset Player Controls.
For information, my joystick is recognized as 'PLAYSTATION(R)3 Controller'
With following configuration :