github: Add DCO/target tests

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>

.github/workflows/commits.yml

@@ -0,0 +1,40 @@
+name: Commits
+on:
+  - pull_request
+
+permissions:
+  contents: read
+
+jobs:
+  dco-check:
+    permissions:
+      pull-requests: read  # for tim-actions/get-pr-commits to get list of commits from the PR
+    name: Signed-off-by (DCO)
+    runs-on: ubuntu-20.04
+    steps:
+    - name: Get PR Commits
+      id: 'get-pr-commits'
+      uses: tim-actions/get-pr-commits@master
+      with:
+        token: ${{ secrets.GITHUB_TOKEN }}
+
+    - name: Check that all commits are signed-off
+      uses: tim-actions/dco@master
+      with:
+        commits: ${{ steps.get-pr-commits.outputs.commits }}
+
+  target-branch:
+    permissions:
+      contents: none
+    name: Branch target
+    runs-on: ubuntu-20.04
+    steps:
+    - name: Check branch target
+      env:
+        TARGET: ${{ github.event.pull_request.base.ref }}
+      run: |
+        set -x
+        [ "${TARGET}" = "master" ] && exit 0
+
+        echo "Invalid branch target: ${TARGET}"
+        exit 1