gitlint: Configure and run on all PRs

Configuration copied from pebble-dev/qemu.

Author: Sorixelle

.github/workflows/gitlint.yaml

@@ -0,0 +1,20 @@
+name: Lint Git Commits
+
+on:
+  pull_request: {}
+
+jobs:
+  lint:
+    runs-on: ubuntu-24.04
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          ref: ${{ github.event.pull_request.head.sha }}
+          fetch-depth: 0
+
+      - name: Install GitLint
+        run: pip install gitlint
+
+      - name: Run GitLint
+        run: gitlint --commits "${{ github.event.pull_request.base.sha }}..HEAD"

.gitlint

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+[general]
+contrib=contrib-body-requires-signed-off-by,contrib-disallow-cleanup-commits
+ignore-merge-commits=false
+ignore-fixup-commits=false
+ignore-fixup-amend-commits=false
+ignore-squash-commits=false
+regex-style-search=true
+
+[ignore-body-lines]
+regex=^\[\d\]: https:\/\/