bug#45198: 28.0.50; Sandbox mode

[Mattias Engdegård]

So far the discussion has been focussed on platform-dependent low-level sandbox 
implementation. I took a stab at writing something that can be used by portable 
code.

It's basically versions of `call-process` and `make-process` specialised for 
running batch-mode Emacs in a sandbox. The attached patch is a straw man 
proposal but that should serve as a starting point for agreement on what the 
interface might look like.

It's only been "tested" on macOS, and there will of course be ERT tests as well 
before it's ready. Everything can be changed.

The idea is to have something that could be used from alpa-admin.el or similar, 
and for running background Elisp byte-compilation.

It uses `make-process` rather than the simpler `start-process` for running an 
asynchronous Emacs because the former seemed to give greater control. There is 
currently only one sandbox parameter: the list of directories to make available 
for reading. Maybe there should be a list of writable directories as well?

We could also consider higher-level primitives, for example something that 
takes a Lisp expression to evaluate and returns the Lisp result, taking care of 
the intermediate printing and reading.

0001-platform-independent-sandbox-interface.patch
Description: Binary data