* guix/scripts/pack.scm (self-contained-tarball/builder)
[extra-options]: New argument.
(self-contained-tarball, squashfs-image, docker-image)
(debian-archive): Likewise. Remove two TODO comments. Document
EXTRA-OPTIONS. Use the custom control files when provided.
(%deb-format-options): New variable.
(show-deb-format-options, show-deb-format-options/detailed): New procedures.
(%options): Register new options.
(show-help): Augment with new usage.
(guix-pack): Validate and propagate new argument values.
* doc/guix.texi (Invoking guix pack)[deb]: Document how to list advanced
options. Add an example.
* tests/pack.scm (deb archive...): Provide extra-options to the debian-archive
procedure, and validate that the provided files are embedded in the pack.
aeded14b83