om show: Display description for flake apps

[shivaraj-bh]

Add our custom schema until DeterminateSystems/flake-schemas#31 is merged.

Merge with official schema.

resolves #163

[shivaraj-bh]

I think this can be replaced with:

DEFAULT_FLAKE_SCHEMAS = flake.inputs.self + /nix/flake-schemas;

It should behave the same since there is no filter provided for cleanSourceWith?

[shivaraj-bh]

@srid why does OM_INIT_REGISTRY use cleanSourceWith if there is no filter?

[srid]

That's the actual semantics of cleanSourceWith,

Proof:

❯ echo $OM_INIT_REGISTRY
/nix/store/9j2sil7h6w2lx7p71x2khhy0ba7v0i9d-flakreate-registry

With,

diff --git a/crates/omnix-cli/crate.nix b/crates/omnix-cli/crate.nix
index 0f99d6d..04043bd 100644
--- a/crates/omnix-cli/crate.nix
+++ b/crates/omnix-cli/crate.nix
@@ -34,11 +34,7 @@ in
         ) ++ lib.optionals pkgs.stdenv.isLinux [
         pkgsStatic.openssl
       ];
-      OM_INIT_REGISTRY =
-        lib.cleanSourceWith {
-          name = "flakreate-registry";
-          src = flake.inputs.self + /crates/flakreate/registry;
-        };
+      OM_INIT_REGISTRY = flake.inputs.self + /crates/flakreate/registry;
       DEVOUR_FLAKE = inputs.devour-flake;
       OMNIX_SOURCE = inputs.self;
       NIX_FLAKE_SCHEMAS_BIN = lib.getExe pkgs.nix-flake-schemas;

That becomes:

❯ echo $OM_INIT_REGISTRY
/nix/store/fsrav4xa7wrhnw19h04r4jk7cdpkbh6g-source/crates/flakreate/registry

@roberth was the one originally came across this pattern, in haskell-flake:

https://github.com/srid/haskell-flake/blob/e48718c26fa9ba2e7c2b3a8e5df2781b64acb011/nix/build-haskell-package.nix#L15-L24

Since this function is not self-documenting (what does "clean source" even mean here?) perhaps there should be another function that is?