fix: prioritize GITEA_SERVER_URL over GITHUB_SERVER_URL for custom Gitea instances

- Modified config.ts to check GITEA_SERVER_URL first, then fall back to GITHUB_SERVER_URL
- Fixes issue where container-based Gitea instances generate internal URLs in comments
- Added comprehensive test suite for URL configuration scenarios
- Updated README.md with configuration documentation and examples
- Added example workflow file for custom URL setup
- Fixed TypeScript configuration to support Node.js globals

Resolves issue #4: Enable GITEA_SERVER_URL environment variable override

test/gitea-server-url.test.ts

@@ -0,0 +1,83 @@
+import { describe, it, expect, beforeEach, afterEach } from "bun:test";
+
+describe("GITEA_SERVER_URL configuration", () => {
+  const originalEnv = process.env;
+
+  beforeEach(() => {
+    // Reset environment variables
+    process.env = { ...originalEnv };
+    delete process.env.GITEA_SERVER_URL;
+    delete process.env.GITHUB_SERVER_URL;
+    
+    // Clear module cache to force re-evaluation
+    delete require.cache[require.resolve("../src/github/api/config")];
+  });
+
+  afterEach(() => {
+    process.env = originalEnv;
+  });
+
+  it("should prioritize GITEA_SERVER_URL over GITHUB_SERVER_URL", async () => {
+    process.env.GITEA_SERVER_URL = "https://gitea.example.com";
+    process.env.GITHUB_SERVER_URL = "http://gitea:3000";
+
+    const { GITEA_SERVER_URL } = await import("../src/github/api/config");
+    expect(GITEA_SERVER_URL).toBe("https://gitea.example.com");
+  });
+
+  it("should fall back to GITHUB_SERVER_URL when GITEA_SERVER_URL is not set", async () => {
+    process.env.GITHUB_SERVER_URL = "http://gitea:3000";
+
+    const { GITEA_SERVER_URL } = await import("../src/github/api/config");
+    expect(GITEA_SERVER_URL).toBe("http://gitea:3000");
+  });
+
+  it("should use default when neither GITEA_SERVER_URL nor GITHUB_SERVER_URL is set", async () => {
+    const { GITEA_SERVER_URL } = await import("../src/github/api/config");
+    expect(GITEA_SERVER_URL).toBe("https://github.com");
+  });
+
+  it("should ignore empty GITEA_SERVER_URL and use GITHUB_SERVER_URL", async () => {
+    process.env.GITEA_SERVER_URL = "";
+    process.env.GITHUB_SERVER_URL = "http://gitea:3000";
+
+    const { GITEA_SERVER_URL } = await import("../src/github/api/config");
+    expect(GITEA_SERVER_URL).toBe("http://gitea:3000");
+  });
+
+  it("should derive correct API URL from custom GITEA_SERVER_URL", async () => {
+    process.env.GITEA_SERVER_URL = "https://gitea.example.com";
+
+    const { GITEA_API_URL } = await import("../src/github/api/config");
+    expect(GITEA_API_URL).toBe("https://gitea.example.com/api/v1");
+  });
+
+  it("should handle GitHub.com URLs correctly", async () => {
+    process.env.GITEA_SERVER_URL = "https://github.com";
+
+    const { GITEA_API_URL } = await import("../src/github/api/config");
+    expect(GITEA_API_URL).toBe("https://api.github.com");
+  });
+
+  it("should create correct job run links with custom GITEA_SERVER_URL", async () => {
+    process.env.GITEA_SERVER_URL = "https://gitea.example.com";
+    
+    // Clear module cache and re-import
+    delete require.cache[require.resolve("../src/github/operations/comments/common")];
+    const { createJobRunLink } = await import("../src/github/operations/comments/common");
+    
+    const link = createJobRunLink("owner", "repo", "123");
+    expect(link).toBe("[View job run](https://gitea.example.com/owner/repo/actions/runs/123)");
+  });
+
+  it("should create correct branch links with custom GITEA_SERVER_URL", async () => {
+    process.env.GITEA_SERVER_URL = "https://gitea.example.com";
+    
+    // Clear module cache and re-import
+    delete require.cache[require.resolve("../src/github/operations/comments/common")];
+    const { createBranchLink } = await import("../src/github/operations/comments/common");
+    
+    const link = createBranchLink("owner", "repo", "feature-branch");
+    expect(link).toBe("\n[View branch](https://gitea.example.com/owner/repo/src/branch/feature-branch/)");
+  });
+});