GELI passphrase and/or key via command line or environment

[grarpamp]

For both init and attach (and even elsewhere where
applicable), I'd like to be able to specify the passphrase
and key material via the command line and/or the environment.
Yes, we have -J/j and -K/k, but they only permit the use of files
or standard in. And of course standard in is not an arbitrary
file descriptor and as such is only usable once. So it cannot
be used with both jay and kay. I use both jay and kay, and want
to do so programmatically without blocking on keyboard input.
In the current implementation, I cannot achieve this.

I'm well aware of all security implications of command line
and environment usage.

Please offer your consideration of this feature request :)
Thanks.