如何在github操作中运行gitdiff

我得到这个：

Command failed: git diff --name-only HEAD^..HEAD
fatal: ambiguous argument 'HEAD^..HEAD': unknown revision or path not in the working tree.

我想git diff --name-only HEAD^..HEAD在我的分支中运行以获取已更改文件的列表。它在本地工作，但不在 GitHub 操作上。我必须做什么？

我的代码是这样的：

name: build
on:
  push:
    branches:
      - main
jobs:
  run:
    name: Build
    runs-on: ubuntu-latest
    steps:
      - name: Checkout repo
        uses: actions/checkout@v2
      - name: Configure Node.js
        uses: actions/setup-node@v2
        with:
          node-version: 14.x
      - name: Install dependencies
        run: yarn install
      - name: Publish file changes to Slack
        # HERE I run `git diff` in node.js process
        run: "SLACK_TOKEN=${{ secrets.GITHUB_TOKEN }} npx ts-node scripts/publishSlackUpdate"
      - name: Build TOC
        run: make toc
      - name: Commit build changes
        uses: EndBug/add-and-commit@v7
        with:
          author_name: Docs Builder
          author_email: docs@mysite.com
          message: 'Updated build'
          add: '*.md'

回答

    # Number of commits to fetch. 0 indicates all history for all branches and tags.
    # Default: 1
    fetch-depth: ''

    steps:
      - name: Checkout repo
        uses: actions/checkout@v2
        with:
          fetch-depth: 2