fix: propagate fatal git errors from hasCommits

src/git/diff.ts

@@ -170,6 +170,33 @@ export async function getStagedDiffWithSignal(
   }
 }
 
+function isUnbornHead(): boolean {
+  let headRef: string;
+  try {
+    headRef = execFileSync(getGitExecutable(), ['symbolic-ref', '--quiet', 'HEAD'], {
+      encoding: 'utf-8',
+      stdio: 'pipe',
+    }).trim();
+  } catch {
+    // A detached or malformed HEAD is not the normal empty-repository state.
+    return false;
+  }
+
+  try {
+    const refs = execFileSync(getGitExecutable(), ['for-each-ref', '--format=%(refname)', headRef], {
+      encoding: 'utf-8',
+      stdio: 'pipe',
+    })
+      .split(/\r?\n/)
+      .filter(Boolean);
+
+    return headRef.length > 0 && !refs.includes(headRef);
+  } catch {
+    // If the ref database cannot be queried, keep the original fatal Git error.
+    return false;
+  }
+}
+
 export function hasCommits(): boolean {
   try {
     const count = execFileSync(getGitExecutable(), ['rev-list', '--count', 'HEAD'], {
@@ -178,8 +205,14 @@ export function hasCommits(): boolean {
     }).trim();
 
     return Number.parseInt(count, 10) > 0;
-  } catch {
-    return false;
+  } catch (err) {
+    if (isUnbornHead()) {
+      return false;
+    }
+
+    const nodeErr = err as NodeJS.ErrnoException & { stderr?: string };
+    const stderr = nodeErr.stderr?.trim();
+    throw new Error(stderr || nodeErr.message || 'Failed to inspect git history');
   }
 }
 

tests/git-diff.test.mjs

@@ -112,6 +112,23 @@ test("hasCommits returns true after the first commit", () => {
   }
 });
 
+test("hasCommits propagates a fatal HEAD error", () => {
+  const repoDir = initRepo();
+
+  try {
+    git(["commit", "--allow-empty", "-m", "initial commit"], repoDir);
+    const headRef = git(["symbolic-ref", "--quiet", "HEAD"], repoDir).trim();
+    const headPath = join(repoDir, ".git", "refs", "heads", headRef.slice("refs/heads/".length));
+    writeFileSync(headPath, "deadbeefdeadbeefdeadbeefdeadbeefdeadbeef\n", "utf-8");
+
+    withCwd(repoDir, () => {
+      assert.throws(() => hasCommits(), /unknown revision|bad object|ambiguous argument/i);
+    });
+  } finally {
+    rmSync(repoDir, { recursive: true, force: true });
+  }
+});
+
 test("getStagedDiff returns diff when changes are staged", () => {
   const repoDir = initRepo();