This sets the state version in recent installs to the latest released
version. It is beneficial for people to be aware of this option and it
is also good to help new users get a more recent setup.
This commit adds a "build" command to the install derivation that
tells the user that `nix-shell` should be used.
A derivation attribute `shellHookOnly = true` is also added with the
intent to indicate that the shell hook is the entire point of the
derivation.
This avoids the uncontrollable nature of fetching the tarball as part
of the evaluation. Instead the user can decide when to update and also
perform rollbacks, if necessary.
In particular, don't bother attempting to do substitution of the home
files and home generation derivations since these rarely, if ever,
could be substituted.
Fixes#330
This changes the installation command from
nix-shell $HM_PATH -A install --run 'home-manager switch'
to
nix-shell $HM_PATH -A install
The added shell hook will print some useful information and run
`home-manager switch`.
