" The 9import tool allows an arbitrary file on a remote system, with the capability of running the Plan 9 exportfs(4) service, to be imported into the local name space. Usually file is a directory, so the complete file tree under the directory is made available."
https://9fans.github.io/plan9port/man/man4/9import.html
9import host1 / /tmp/host1
9import host2 /tmp/host2
diff /tmp/host1/a/b/c /tmp/host2/a/b/c
(or whatever command you want that works with files. No need for stuff like 'rdiff' etc.)
stuff you take for granted on some systems ...
I have the plan 9 cpu command working (written in Go) and I think it's time I get import working more widely, it's just too useful.