On December 6, 2020, Ricardo Wurmus <rekado@elephly.net> wrote:

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.

These suggestions comport nicely with the Unix-philosophy and something like that should probably be implemented for people who want to build their own deploy systems like you're describing.

Additionally, I think that the use-case of "deploy this software to some server that doesn't have Guix installed" is important enough that we might want to support it explicitly such that "guix deploy" does the right thing, doing minimal work to bring the target deployment up-to-date. Is that feasible?