As discussed in
<https://github.com/nix-community/home-manager/issues/5069>.
I set `ExecStart=%install_dir%/himalaya` so when packaging himalaya
people nee to explicitly set the path to himalaya (i.e. `sed
's:%install_dir%:/usr/bin:' assets/himalaya-watch@.service`). This is
done automatically in `install.sh` if `$PREFIX` is `/usr`, Otherwise
the packager should handle it themselves
For `nix` it would be (`sed 's:%install_dir%:$out/bin:'
assets/himalaya-watch@.service`). I don't know where it should be placed
(probably `$out/share/systemd/user` as nix will add that to
`$XDG_DATA_DIRS` which is searched by `systemctl --user`.
I swear I checked the address like 4 times before sending the email, I
have no idea how I managed to mess it up T-T. I was wondering why the
formatting was so messed up in sr.ht.
* Replace echo with printf
The echo(1) command varies among sh implementations. Some interpret
hyphen command-line options.
It would be unusual, but in theory if $PREFIX began with a hyphen or
two then this usage of echo might cause an error or unknown behaviour
in such implementations.
The printf(1) command is consistent across shell implementations.
* Leave privilege elevation to the user
* Add die function
* Break long line
