guix pack file enumerator?

[Ricardo Wurmus <rekado@elephly.net>]

Hi Guix,

“guix pack” is great for deployment of applications to servers that
don’t have Guix.  For a project I have a “deploy” target in my Makefile
that essentially does this:

    cat $(shell guix pack -RR -e '(load "guix.scm")' -S /bin=bin) | ssh remote-server "tar xvzf - -C /where/i/want/it"

This is fine for small deployments, but it’s a little annoying that it
transfer *all* the files, even those that haven’t changed.  So I thought
I could use rsync here, but it’s inconvenient that “guix pack” will do
what it was designed for and produce a single file bundle.

What do you think about adding an output format that is no format at all
but a file enumeration printed to stdout?  That way I could use “guix
pack” to produce a list of files to transfer and use that to transfer
only the unchanged files.  Alternatively, perhaps we could have a
“directory” format that merely copies (or links) the files to a new
directory root.

-- 
Ricardo