ci: Add test-each-commit task

.github/workflows/ci.yml

@@ -23,6 +23,20 @@ env:
   MAKEJOBS: '-j10'
 
 jobs:
+  test-each-commit:
+    name: 'test each commit'
+    runs-on: ubuntu-22.04
+    if: github.event_name == 'pull_request'
+    timeout-minutes: 360  # Use maximum time, see https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#jobsjob_idtimeout-minutes
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          ref: ${{ github.event.pull_request.head.sha }}
+          fetch-depth: '0'
+      - run: git checkout HEAD~  # Skip the top commit, because it is already checked by the other tasks.
+      - run: sudo apt install ccache build-essential libtool autotools-dev automake pkg-config bsdmainutils python3-zmq libevent-dev libboost-dev libsqlite3-dev libdb++-dev systemtap-sdt-dev libminiupnpc-dev libnatpmp-dev libqt5gui5 libqt5core5a libqt5dbus5 qttools5-dev qttools5-dev-tools qtwayland5 libqrencode-dev -y
+      - run: EDITOR=true git rebase --interactive --exec "./autogen.sh && CC=clang CXX=clang++ ./configure && make clean && make -j $(nproc) check && ./test/functional/test_runner.py -j $(( $(nproc) * 2 ))" $( git log --merges -1 --format='%H' )
+
   macos-native-x86_64:
     name: 'macOS 13 native, x86_64, no depends, sqlite only, gui'
     # Use latest image, but hardcode version to avoid silent upgrades (and breaks).