feat(apps): add to nixFastBuild and clean up nix code

apps/update-sources/src/flake.ts

@@ -0,0 +1,35 @@
+import { spawnSync } from 'node:child_process';
+
+
+/* Constants */
+const FLAKE = process.env.FLAKE;
+
+export const updateFlakeInputs = () => {
+    const output = spawnSync(
+        `git restore flake.lock &> /dev/null; nix flake update --flake ${FLAKE}` +
+        ' |& grep -v "warning: updating lock file" |& grep -v "unpacking"',
+        [],
+        { shell: true },
+    ).stdout
+        .toString()
+        // Add an extra blank line between inputs
+        .split('\n•')
+        .filter((input) => ![
+            'systems',
+            'flake-utils',
+            'flake-parts',
+            'treefmt-nix',
+            'lib-aggregate',
+            'lib-aggregate/nixpkgs-lib',
+            'sops-nix/nixpkgs-stable',
+        ].some((inputName) => input.startsWith(` Updated input '${inputName}'`)))
+        .join('\n\n•')
+        // Shorten git revs to help readability
+        .split('\n')
+        .map((l) => l
+            .replace(/.{33}\?narHash=sha256[^']*/, '')
+            .replace(/&rev=(.{7})[^'&]*/, (_, backref) => `&rev=${backref}`))
+        .join('\n');
+
+    return output;
+};