fix: stop retrying deterministic ref updates (#1551)

test/update-git-reference.test.ts

@@ -0,0 +1,90 @@
+import { describe, expect, it } from "bun:test";
+import { GITHUB_API_URL } from "../src/github/api/config";
+import { updateGitReference } from "../src/mcp/update-git-reference";
+
+const reference = {
+  owner: "owner",
+  repo: "repo",
+  branch: "feature",
+  sha: "abc123",
+  githubToken: "token",
+};
+
+function response(status: number) {
+  return {
+    ok: status >= 200 && status < 300,
+    status,
+    text: async () => "response body",
+  };
+}
+
+describe("updateGitReference", () => {
+  it("should patch the branch reference", async () => {
+    await updateGitReference({
+      ...reference,
+      fetchFn: async (url, init) => {
+        expect(url).toBe(
+          `${GITHUB_API_URL}/repos/owner/repo/git/refs/heads/feature`,
+        );
+        expect(init.method).toBe("PATCH");
+        expect(init.headers).toMatchObject({ Authorization: "Bearer token" });
+        expect(JSON.parse(String(init.body))).toEqual({
+          sha: "abc123",
+          force: false,
+        });
+        return response(200);
+      },
+    });
+  });
+
+  it("should not retry deterministic client errors", async () => {
+    for (const status of [400, 404, 409, 422]) {
+      let attempts = 0;
+
+      await expect(
+        updateGitReference({
+          ...reference,
+          fetchFn: async () => {
+            attempts++;
+            return response(status);
+          },
+          retryOptions: { initialDelayMs: 1 },
+        }),
+      ).rejects.toThrow(`Failed to update reference: ${status}`);
+
+      expect(attempts).toBe(1);
+    }
+  });
+
+  it("should retry transient HTTP errors", async () => {
+    for (const status of [403, 429, 500]) {
+      let attempts = 0;
+
+      await updateGitReference({
+        ...reference,
+        fetchFn: async () => response(attempts++ === 0 ? status : 200),
+        retryOptions: { initialDelayMs: 1 },
+      });
+
+      expect(attempts).toBe(2);
+    }
+  });
+
+  it("should retry network errors", async () => {
+    let attempts = 0;
+
+    await updateGitReference({
+      ...reference,
+      fetchFn: async () => {
+        attempts++;
+        if (attempts === 1) {
+          throw new Error("network error");
+        }
+        return response(200);
+      },
+      retryOptions: { initialDelayMs: 1 },
+    });
+
+    expect(attempts).toBe(2);
+  });
+});