Add isGhes gate and refactor to clean up circular dependencies

packages/cache/__tests__/config.test.ts

@@ -0,0 +1,26 @@
+import { promises as fs } from 'fs'
+import * as config from '../src/internal/config'
+
+beforeEach(() => {
+    jest.resetModules()
+})
+
+test('isGhes returns false for github.com', async () => {
+    process.env.GITHUB_SERVER_URL = 'https://github.com'
+    expect(config.isGhes()).toBe(false)
+})
+
+test('isGhes returns false for ghe.com', async () => {
+    process.env.GITHUB_SERVER_URL = 'https://somedomain.ghe.com'
+    expect(config.isGhes()).toBe(false)
+})
+
+test('isGhes returns true for enterprise URL', async () => {
+    process.env.GITHUB_SERVER_URL = 'https://my-enterprise.github.com'
+    expect(config.isGhes()).toBe(true)
+})
+
+test('isGhes returns false for ghe.localhost', () => {
+    process.env.GITHUB_SERVER_URL = 'https://my.domain.ghe.localhost'
+    expect(config.isGhes()).toBe(false)
+})