Since the formatter always depended on devShell packages, building the
formatter involved building all the devShell packages, which can be
slow.
In the case where formatters are set to plain strings, such as
"nixpkgs-fmt", depending on the devShell packages is necessary in order
to put the formatting utility on the path. But when a formatters option
is set to an package, such as "${pkgs.nixpkgs-fmt}/bin/nixpkgs-fmt",
then that formatter option does not depend on the devShell packages.
Flakelight now detects if any of the configured formatters are using the
first form, and only if so does it add the devShell packages dependency.
This allows the first form to still work, without incurring a cost for
flakes that only use the second form.
Users can use the second form for all formatters options if they wish to
not build the devShell packages when using the formatter.
`devShell` accepted either a package def, a submodule value, or a
function to a submodule value. `devShells` only accepted package defs.
This brings all the options of `devShells` to any devShell configured
with `devShells`.
Before, devShell could be set to a submodule config, a package def, or a
function taking module args and returning a submodule config. This
changes the last form to take the package set instead.
This enables cleaner configuration by not needing each option to
individually be a function of pkgs. Passing pkgs also gives more
flexibility as all the module args are available under the `moduleArgs`
attr.
Code that relied on module args not directly in the package set will now
have to access them from the `moduleArgs` attr.
Instead of having to call the configuration generation functions, the
params can just be set, and the functions will be called automatically
with additional useful settings automatically set.
The `propagationModule` config option provides a module that can be used
to propagate flakelight configuration into other module systems such as
NixOS or home-manager.
In order to speed up evalutation of flakes setting `packages.default`,
this trys to compute the pname in multiple ways, ordered by speed. The
pname can be set manually, which is fastest. To avoid computing a new
nixpkgs and flakelight overlays, the second option just uses callPackage
from stock nixpkgs. If that fails, the prior, most accurate, method is
used which creates a new nixpkgs with all the overlays available.
The set of args passed to modules is useful for more than just
autoloading. This renames it appropriately and makes it available
through pkgs arguments as well.
