Unfortunately systemd derives nonsensical unit names when the unit
file is a link to a link to a file. This commit ensures that any file
whose target path matches the pattern `*/systemd/user/*` will be
reachable with only one link hop.
This also reverts f52ec0df7c, which
contained a temporary fix. This commit is an improvements in that it
is more explicit and also handles unit files given directly as a home
file source.
This is done by exploiting the fact that home files will be copied if
the executable bit of the source file and the target file is
different. This should be considered a hack until some nicer solution
is found.
Note, we still pull in the user's `PATH` in case the user has defined
their own activation blocks that depend on additional tools.
Eventually this will be deprecated and removed.
See #99.
This commit causes an error to be printed if running under a non-Linux
system when a systemd service, target, or timer is active.
It will also prevent running systemd during activation if running
under a non-Linux system.
