Try cloning without actions/checkout

README.md

@@ -27,17 +27,6 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      # Perform a minimal checkout to set up this repository for the rest of the
-      # workflow.
-      #
-      # This step must be configured exactly as below: using different
-      # actions/checkout arguments is not supported.
-      - name: Checkout this repository
-        uses: actions/checkout@v4
-        with:
-          filter: tree:0
-
-      # Run the estimation tool
       - name: Run sizeup
         # TODO: Replace the version below with your desired version.
         uses: lerebear/sizeup-action@v0.4.2

__tests__/main.test.ts

@@ -9,21 +9,31 @@
 import * as core from '@actions/core'
 import * as main from '../src/main'
 import * as initializer from '../src/initializer'
+import { Git } from '../src/git'
 import * as github from '@actions/github'
 
 function pullRequestEventContext(overrides = {}): object {
   return {
     eventName: 'pull_request',
+    repo: {
+      owner: 'lerebear',
+      name: 'sizeup-action'
+    },
     payload: {
       pull_request: {
         base: {
+          ref: 'main',
           repo: {
+            full_name: 'lerebear/sizeup-action',
             name: 'sizeup-action',
             owner: {
               login: 'lerebear'
             }
           }
         },
+        head: {
+          ref: 'topic'
+        },
         labels: [],
         number: 1,
         user: {
@@ -69,9 +79,12 @@ describe('action', () => {
   // Shallow clone original @actions/github context
   const originalContext = { ...github.context }
 
+  // Mock cloning the repo
+  jest.spyOn(Git.prototype, 'clone').mockImplementation(async () => {})
+
   // Mock the diff that we use for evaluation.
   jest
-    .spyOn(initializer, 'fetchDiff')
+    .spyOn(Git.prototype, 'diff')
     .mockImplementation(async () =>
       Promise.resolve(
         '--- README.md	2023-10-16 16:35:38\n+++ README-AGAIN.md	2023-10-16 16:36:07\n@@ -0,0 +1 @@\n+# Hello, World!'

src/git.ts

@@ -0,0 +1,70 @@
+import * as core from '@actions/core'
+import * as lib from 'simple-git'
+
+export class Git {
+  private client: lib.SimpleGit
+
+  constructor() {
+    const basicCredential = Buffer.from(
+      `x-access-token:${core.getInput('token')}`,
+      'utf8'
+    ).toString('base64')
+    const authorizationHeader = `AUTHORIZATION: basic ${basicCredential}`
+    core.setSecret(basicCredential)
+
+    this.client = lib.simpleGit('.', {
+      trimmed: true,
+      config: [`http.extraheader=${authorizationHeader}`]
+    })
+  }
+
+  /**
+   * Clones the repository from which this workflow was triggered.
+   *
+   * @param repo The repository to clone in the format "<owner>/<name>"
+   * @param headRef The single branch to clone, which should correspond to the
+   *   head ref of the pull request that triggered this workflow. This is
+   *   required for efficiency.
+   * @param targetDirectory The directory in which to clone the repository.
+   */
+  async clone(
+    repo: string,
+    headRef: string,
+    targetDirectory = '.'
+  ): Promise<void> {
+    core.info(`Cloning ${repo} with the single branch "${headRef}"`)
+
+    await this.client.clone(`https://github.com/${repo}`, targetDirectory, [
+      `--branch=${headRef}`,
+      '--filter=tree:0',
+      '--no-tags',
+      '--single-branch'
+    ])
+  }
+
+  /**
+   * Retrieves the diff of the pull request that triggered this workflow which we
+   * will use for evaluation.
+   *
+   * @param baseRef The base branch relative to which we should produce a diff. This method assumes
+   *   that the head ref containing the changes has already been fetched.
+   * @returns The diff of the given pull request or `undefined` if we failed to retrieve it.
+   */
+  async diff(baseRef: string): Promise<string | undefined> {
+    core.debug(`Fetching base ref "${baseRef}"`)
+    await this.client.fetch([
+      'origin',
+      `+${baseRef}:${baseRef}`,
+      `--filter=tree:0`,
+      '--no-tags',
+      '--prune',
+      '--no-recurse-submodules'
+    ])
+
+    const diffArgs = ['--merge-base', baseRef].concat(
+      core.getInput('git-diff-options').split(/\s+/)
+    )
+    core.info(`Retrieving diff with \`git diff ${diffArgs.join(' ')}\``)
+    return this.client.diff(diffArgs)
+  }
+}