Manage files by creating a systemd oneshot service for each file. The
service links or bind mounts the file as appropriate on start and
removes the link or unmounts it when stopped. Whether a symlink or
bind mount is used is determined by if the target exists - if it does,
it's bind mounted, otherwise symlinked. To make sure files are
available early enough, also run the start portion in the activation
script.
This lifts the restriction on files being placed in `/etc` and should
finally close#1.
NixOS defaults to not letting fuse mounts be allowed to let other
users read their contents. `bindfs` wants to give other users access
and is therefore normally run with `--no-allow-other` to not throw an
error.
Giving other users, mainly `root`, access to the bind mounts is,
however, useful and works fine when
programs.fuse.userAllowOther = true;
is declared in `configuration.nix`. This adds an option to choose
whether to give other users access or not. It also prompts the user to
set the `allowOther` attribute with a link to the documentation.
