Log warnings instead of silently swallowing git errors in getDiff/getDiffStats (#84)

Add console.warn with worktree path and error message when git commands
fail, instead of empty catch blocks. Return values unchanged (empty
diff/stats) so pipeline continues. 2 new tests verify warnings are emitted.

Generated by thinktank (5 agents, 70% convergence, Agent #4 recommended).

Closes #66

Co-authored-by: unknown <that-github-user@github.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: 3 people

src/utils/git.test.ts

@@ -55,3 +55,37 @@ describe("cleanupBranches", () => {
     // Should not throw
   });
 });
+
+describe("getDiff warning on failure", () => {
+  it("warns to stderr and returns empty string for invalid worktree path", async () => {
+    const warnings: string[] = [];
+    const originalWarn = console.warn;
+    console.warn = (...args: unknown[]) => warnings.push(args.join(" "));
+    try {
+      const result = await getDiff("/nonexistent/path/thinktank-test");
+      assert.equal(result, "");
+      assert.equal(warnings.length, 1);
+      assert.ok(warnings[0].includes("getDiff failed"));
+      assert.ok(warnings[0].includes("/nonexistent/path/thinktank-test"));
+    } finally {
+      console.warn = originalWarn;
+    }
+  });
+});
+
+describe("getDiffStats warning on failure", () => {
+  it("warns to stderr and returns empty stats for invalid worktree path", async () => {
+    const warnings: string[] = [];
+    const originalWarn = console.warn;
+    console.warn = (...args: unknown[]) => warnings.push(args.join(" "));
+    try {
+      const result = await getDiffStats("/nonexistent/path/thinktank-test");
+      assert.deepEqual(result, { filesChanged: [], linesAdded: 0, linesRemoved: 0 });
+      assert.equal(warnings.length, 1);
+      assert.ok(warnings[0].includes("getDiffStats failed"));
+      assert.ok(warnings[0].includes("/nonexistent/path/thinktank-test"));
+    } finally {
+      console.warn = originalWarn;
+    }
+  });
+});

src/utils/git.ts

@@ -46,7 +46,10 @@ export async function getDiff(worktreePath: string): Promise<string> {
       cwd: worktreePath,
     });
     return stdout;
-  } catch {
+  } catch (err) {
+    console.warn(
+      `[thinktank] getDiff failed for worktree ${worktreePath}: ${err instanceof Error ? err.message : String(err)}`,
+    );
     return "";
   }
 }
@@ -76,7 +79,10 @@ export async function getDiffStats(
     }
 
     return { filesChanged, linesAdded, linesRemoved };
-  } catch {
+  } catch (err) {
+    console.warn(
+      `[thinktank] getDiffStats failed for worktree ${worktreePath}: ${err instanceof Error ? err.message : String(err)}`,
+    );
     return { filesChanged: [], linesAdded: 0, linesRemoved: 0 };
   }
 }