scan-licenses: create a merge request updating the copyright file on default branch only

This is especially useful during a rebase where the copyright
tooling is updated and the copyrght file needs to be refreshed.
Some packages don't have any update in the next Debian release,
but the pipeline fails only because we have to manually refresh
the copyright file, so let's it create a MR to save us time.

Signed-off-by: Dylan Aïssi <dylan.aissi@collabora.com>

ci-package-builder.yml

@@ -571,6 +571,31 @@ scan-licenses:
     - dpkg-source --after-build .
     - |
       case $BRANCH in
+        $CI_DEFAULT_BRANCH)
+          if ! diff debian/apertis/copyright.new debian/apertis/copyright
+          then
+            echo "Copyright report needs to be updated, creating a MR"
+            NEW_BRANCH=proposed-copyright-updates/$CI_COMMIT_SHORT_SHA
+            git checkout -b $NEW_BRANCH
+            mv debian/apertis/copyright.new debian/apertis/copyright
+            git add -f debian/apertis/copyright
+            git commit -s -m 'Refresh the automatically detected licensing information' debian/apertis/copyright
+            dch -i -m 'Refresh the automatically detected licensing information' -D apertis --force-distribution
+            git add -f debian/changelog
+            NEW_VERSION=$(dpkg-parsechangelog -SVersion)
+            git commit -s -m "Release $PACKAGE version $NEW_VERSION"
+            git push -o merge_request.create \
+                     -o merge_request.remove_source_branch \
+                     -o merge_request.target=$CI_DEFAULT_BRANCH \
+                     -o merge_request.target_project=$CI_PROJECT_PATH \
+                     -o merge_request.title='Refresh the automatically detected licensing information' \
+                     ${CI_AUTH_PROJECT_URL} HEAD:${NEW_BRANCH}
+            exit 1
+          else
+            echo "Copyright report is up to date"
+          fi
+          rm debian/apertis/copyright.new
+        ;;
         $OSNAME/*)
           if ! diff debian/apertis/copyright.new debian/apertis/copyright
           then