* format: improve argument handling
For now, fail if the user tries to format a specific file/directory,
or runs the formatter from within a subdirectory.
Handling these situations is slightly tricky because `find -path` is
not very flexible.
* flake: add formatter
This allows running the formatter with `nix fmt`, added in Nix 2.8.
* format: use git ls-files
This is cleaner than `find` and allows us to restrict formatting to
particular files or subdirectories.
* Add flake.lock and clean up flake.nix
Add a lockfile to work around https://github.com/NixOS/nix/issues/6541
(and because it's a good idea anyway).
Also use flake-utils, and restrict ourselves to the five platforms
supported by nixpkgs. Otherwise, the IFD for nmd fails on weird
platforms. This fixes `nix flake check`.
Remove the redundant `apps` output, see https://github.com/nix-community/home-manager/pull/2442#issuecomment-1133670487
* nixos,nix-darwin: factor out into a common module
* nixos,nix-darwin: make `home-managers.users` shallowly visible
Make sure the option is included in the NixOS/nix-darwin manual (but the
HM submodule options aren't).
Also add a static description to the HM submodule type so that we don't need to
evaluate the submodules just to build the option manual. This makes
nixos-search able to index the home-manager flake.
Also clean up some TODOs.
* flake: add nmd and nmt
This avoids having to use `pkgs.fetchFromGitLab` in an IFD, which causes
issues when indexing packages with nixos-search because `pkgs` is
instantiated with every platform.
Removed format exclusion exceptions for modules that are already
formatted correctly (that is, when running nixfmt, no changes happen) or
have been moved (in the case of i3.nix).
The format script can be used to automatically format the Nix source
files and also verify that the files are formatted using the `-c`
command argument.
At the moment some files are exempt from the formatting to avoid
causing merge conflicts in active pull requests.
Finally, update the contribution guidelines to note that `nixfmt`
should be used.
