Extract paired source ref helpers

src/paired-source-ref.ts

@@ -0,0 +1,45 @@
+import { execFileSync } from 'child_process';
+
+export function resolveCanonicalSourceRef(workDir: string): string {
+  const treeHash = resolveCanonicalTreeHash(workDir);
+  return treeHash || 'HEAD';
+}
+
+function resolveCanonicalTreeHash(workDir: string): string | null {
+  try {
+    const treeHash = execFileSync('git', ['rev-parse', 'HEAD^{tree}'], {
+      cwd: workDir,
+      encoding: 'utf-8',
+      stdio: ['ignore', 'pipe', 'pipe'],
+    }).trim();
+    return treeHash || null;
+  } catch {
+    return null;
+  }
+}
+
+export function hasCodeChangesSinceRef(
+  workDir: string,
+  sourceRef: string | null | undefined,
+): boolean | null {
+  if (!sourceRef) return null;
+  try {
+    execFileSync('git', ['diff', '--quiet', sourceRef, 'HEAD'], {
+      cwd: workDir,
+      stdio: ['ignore', 'pipe', 'pipe'],
+    });
+    return false;
+  } catch (error) {
+    const exitCode =
+      typeof error === 'object' &&
+      error !== null &&
+      'status' in error &&
+      typeof (error as { status?: unknown }).status === 'number'
+        ? (error as { status: number }).status
+        : null;
+    if (exitCode === 1) {
+      return true;
+    }
+    return null;
+  }
+}