ci: run gitlint on PR title (#1597)

* ci: run gitlint on PR title
* ci: remove fetch-depth from checkout action

Author: rhythmrx9

.github/workflows/linting.yml

@@ -15,8 +15,6 @@ jobs:
         tool: ['isort', 'black', 'pyupgrade', 'flake8', 'bandit', 'gitlint']
     steps:
       - uses: actions/checkout@v2
-        with:
-          fetch-depth: 0
       - uses: actions/setup-python@v2
         with:
           cache: 'pip'
@@ -34,4 +32,4 @@ jobs:
         if: ${{ github.event_name == 'pull_request' && matrix.tool == 'gitlint' }}
         run: |
           python -m pip install --upgrade gitlint
-          gitlint --commits ${{ github.event.pull_request.base.sha }}..${{ github.event.pull_request.head.sha }}
+          echo ${{ github.event.pull_request.title }} | gitlint