There is nothing in this commit except for the changes made by
nix-shell -p nixfmt-rfc-style --run "nixfmt ."
If this has mucked up your open branches then sorry about that. You
can probably nixfmt them to match before merging
* [] is now [ ]
* {} is now { }
* commas in arglists go at end of line not beginning
In short, I ran the whole thing through nixfmt-rfc-style but only
accepted about 30% of its changes. I might grow accustomed to more
of it over time
This requires adding LFS as a dependency because native Lua has
no way to iterate a directory, but it seems to be Not Huge and
hopefully we'll have other uses for it
Previously: the service wrote a timestamp and the receiver
read and parsed it to see if there was new data
Now: the service writes and removes a .lock file to prevent
the receiver reading partial data. The receiver is responsible
for remembering the *previous* state and only updating if it's changed
