How this would work?

- New option on mimeview contextual menu for text/x-patch attachments, for example: "Apply patch to..."
- On clicking a small dialog opens:
  +--------------------------------+
  | Apply patch <attachment name>  | # dialog title
  | To [________________] [Browse] | # path selector
  | Apply with (·) Git ( ) Patch   | # select how to apply
  | Level [v][  1]                 | # conditional dropdown with patch level (0, 1, 2, ...)
  |               [Cancel] [Apply] | # enabled when patch radio option is selected
  +--------------------------------+ 
- It chdirs to the selected path and invokes either 'git am' or 'patch' with those arguments :)
- If git or patch are not in $PATH the corresponding radio button is disabled
- If none of them are in $PATH the menu option appears disabled
- Last selected patch should be remembered

Sounds it good?

Thanks in advance! ;-)