Add a header check to the CI Fix rucio#4980

The `add_header` script needs to be run after an edit to determine the status of
the header and, if necessary, change the header.

This commit adds the check for the header to the CI/CD. This enforces the usage
of the `add_header` script and ensures a healthy code base.

.github/workflows/autotest.yml

@@ -5,6 +5,24 @@ on:
   - push
 
 jobs:
+  header-lint:
+    if: 'github.event_name == ''pull_request'''
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
+      - name: Check headers
+        run: |
+          git pull origin master
+          echo "Current git rev $(git rev-parse HEAD)"
+          echo "Common ancestor git rev $(git merge-base HEAD remotes/origin/master)"
+          echo "If a file header needs to be changed run 'tools/add_header -i FILE' from the rucio project directory."
+          FILES=$(git diff --name-status HEAD $(git merge-base HEAD remotes/origin/master) | grep -v '^A' | cut -f 2 | grep -E '\.py$|^bin/')
+          echo "Files to check: $FILES"
+          if [[ -n $FILES ]]; then
+            tools/add_header --disable-add-me -cd $FILES
+          fi
   setup:
     runs-on: ubuntu-latest
     steps: