Running pre-commit in GitHub workflow on pull request

I am currently using Azure DevOps and am migrating to GitHub. We have one pipeline that runs when a pull request in made active as it first caches the files, compares the main branch to the feature branch, and runs pre-commit on those changed files.

The ADO pipeline looks like:

---
# Pipeline to run pre-commit hooks

trigger: none

pool:
  vmImage: ubuntu-latest

variables:
  PRE_COMMIT_HOME: $(Pipeline.Workspace)/pre-commit-cache

steps:
  - checkout: self
    persistCredentials: true

  - bash: echo "##vso[task.setvariable variable=PY]`python -V`"
    displayName: Get python version
  - task: CacheBeta@0
    inputs:
      key: pre-commit | .pre-commit-config.yaml | "$(PY)"
      path: $(PRE_COMMIT_HOME)

  - bash: |
      git remote set-head origin --auto
      [[ -n "${SYSTEM_PULLREQUEST_TARGETBRANCH}" ]] && COMPARE_BASE="origin/${SYSTEM_PULLREQUEST_TARGETBRANCH#refs/heads/}"
      CHANGED_FILES=`git diff-tree --diff-filter=ACMRT --name-only -r ${COMPARE_BASE:-origin/HEAD}..${BUILD_SOURCEVERSION}`
      if [[ -z "${CHANGED_FILES}" ]]; then
        echo '##vso[task.logissue type=error]Can not detect changed files'
        echo '##vso[task.complete result=Failed;]'
      else
        for file in ${CHANGED_FILES}; do
          echo "##[debug]${file}"
        done
        sudo ln -s /usr/bin/pwsh /usr/bin/powershell
        pip install --quiet pre-commit
        pre-commit run --files ${CHANGED_FILES} || echo "Exit status is $?"
      fi
    env:
      AZURE_DEVOPS_EXT_PAT: $(System.AccessToken)
    displayName: 'Run pre-commit'

  - pwsh: |
      # Construct the REST URL to obtain Build ID
      $uri = "$(System.TeamFoundationCollectionUri)/$(System.TeamProjectId)/_apis/build/builds/$(Build.BuildId)/logs/8?api-version=6.0"

      # Invoke the REST call and capture the results
      Write-Output "Getting the logs from the following URI: $uri"
      $log= Invoke-RestMethod -Uri $uri -Method Get -ContentType "application/json" -Headers @{Authorization = "Bearer $Env:SYSTEM_ACCESSTOKEN"}
      $logs

      if($log -match "exit code: 1")
      {
        Write-Host "##vso[task.setvariable variable=testsStatus]failed"
        # Option 1: fail the pipeline
        Write-Error "The tests not passed! Please check Run pre-commit step for details"
      } elseif ($log -match "exit code: 3") {
        Write-Host "##vso[task.setvariable variable=testsStatus]succeeded"
        Write-Output "Succeeded with exit code 3 - baseline file update"
      } else {
        Write-Output "No error codes found in pre-commit. Tests passed successfully"
      }
    env:
      SYSTEM_ACCESSTOKEN: $(System.AccessToken)
    displayName: 'Check pre-commit status'

I am new to using GitHub actions and so far I have:

name: Pre-commit

on:
  pull_request:
    branches: [ "main" ]
  workflow_dispatch:

jobs:
  build:
    runs-on: ubuntu-latest

    steps:
      - uses: actions/checkout@v3
        with:
          fetch-depth: 0

      - name: set PY
        run: echo "PY=$(python -VV | sha256sum | cut -d' ' -f1)" >> $GITHUB_ENV
      - uses: actions/cache@v1
        with:
          path: ~/.cache/pre-commit
          key: pre-commit|${{ env.PY }}|${{ hashFiles('.pre-commit-config.yaml') }}
          
      - name: Get changed files
        id: changes
        run: |
          echo "::set-output name=all::$(git diff --name-only --diff-filter=ACMRT ${{ github.event.pull_request.base.sha }} ${{ github.sha }} | xargs)"
          
  lint:
    runs-on: ubuntu-latest
    needs: build
    steps:
      - name: echo changed files
        shell: bash
        run:
          git remote set-head origin --auto
          sudo ln -s /usr/bin/pwsh /usr/bin/powershell
          pip install --quiet pre-commit
          pre-commit run --files ${{needs.build.outputs.all}} || echo "Exit status is $?"

With this GitHub action I am getting an error in the lint job saying fatal: not a git repository (or any of the parent directories): .git. Is the issue within the lint job or a syntax elsewhere? The first job does not give any errors or telling messages.

>Solution :

Every jobs run in isolated context so you should checkout the code in the lint one. So, as example:

  lint:
    runs-on: ubuntu-latest
    needs: build
    steps:
      - uses: actions/checkout@v3
        with:
          fetch-depth: 0
      - name: echo changed files
        shell: bash

As suggestion about linting only changed files, I would suggest to refactor your workflow in order to use the dorny/paths-filter action, that is suited for that (See the Real world usage examples)