chore(build): run only the tests related to a push in the pre-push hook

.husky/pre-push

@@ -1 +1,7 @@
-pnpm run prepush 2>&1
+# Run lint, typecheck and the frontend build, then the tests related to what the push changes. The full suite is CI's job: it runs there on every pull request, so repeating it here only repeats the same work for each push attempt, and again for each attempt that fails.
+# The related tests are those vitest finds from the module graph for the files changed since the push diverged from origin/main, and a push that changes no source file has none to run, which is a pass. A change to the vitest config, package.json or the lockfile still reruns everything, as vitest treats those as triggers.
+# Workers are the cores the machine's run queue leaves free, and at least one: vitest starts a pool the size of the core count by default, so several pushes at once on a shared machine each oversubscribe it, and every test slows until the guards against a hang fire on tests that did nothing wrong.
+base=$(git merge-base origin/main HEAD) &&
+workers=$(node -p "Math.max(1, os.availableParallelism() - Math.ceil(os.loadavg()[0]))") &&
+pnpm run prepush 2>&1 &&
+pnpm exec vitest run --changed "$base" --passWithNoTests --maxWorkers="$workers" 2>&1

turbo.json

@@ -17,11 +17,14 @@
       "inputs": ["$TURBO_DEFAULT$", "eslint.config.ts"]
     },
     "_prepush": {
-      "dependsOn": ["_lint", "_typecheck", "_test"]
+      // The checks the pre-push hook runs before its related-tests run. The build is here because the web-bridge
+      // integration tests the hook may select need it (see _test), and turbo caches it, so it costs nothing when
+      // the frontend sources are unchanged.
+      "dependsOn": ["_lint", "_typecheck", "_build:frontend"]
     },
     "_test": {
-      // The web-bridge integration tests request the frontend routes, which serve src/bridges/user/web/dist
-      // -- without this dependency, a fresh checkout with no prior build (a new worktree's pre-push hook, in
+      // The web-bridge integration tests request the frontend routes, which serve src/bridges/user/web/dist.
+      // Without this dependency, a fresh checkout with no prior build (a new worktree running the tests, in
       // particular) gets 503 from those routes and fails those suites rather than actually exercising them.
       "dependsOn": ["_build:frontend"]
     },