[O] customizable org-attach commands?

[Eric Abrahamsen]

I'd like to provide a patch making the org-attach dispatcher
customizable. ie a new custom option `org-attach-commands' that maps
characters to functions, and then the dispatch function builds its menu
from that option. Would that be acceptable?

What I'm trying to do is add my own org-attach function that prompts for
a file and then attaches it to an outgoing Gnus message buffer.

Another org-attach thing I'd like to do is add a way to export a subtree
as a file into the subtree's attach directory, but I haven't come up
with a good way of doing that yet. One way would be to add an option to
the export dispatcher, which seems awkward. Another way would be to
allow a property like ":EXPORT_FILE_NAME: :ATTACH_DIR", and look for
that in `org-export-output-file-name'. But that will require a little
more thought.

Eric