Add a pip install workflow

.github/workflows/pip.yml

@@ -0,0 +1,104 @@
+name: Pip install Firedrake
+
+on:
+  # Push to master or PR
+  push:
+    branches:
+      - master
+  pull_request:
+
+concurrency:
+  # Cancels jobs running if new commits are pushed
+  group: >
+    ${{ github.workflow }}-
+    ${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  build:
+    name: "Build Firedrake"
+    # Run on our self-hosted machines
+    runs-on: ubuntu-latest
+    container:
+      image: firedrakeproject/firedrake-env:latest
+    strategy:
+      # Don't immediately kill real if complex fails and vice versa.
+      fail-fast: false
+      matrix:
+        include:
+          - scalar-type: real
+            petsc_arch: default
+          - scalar-type: complex
+            petsc_arch: complex
+    env:
+      # PETSC_DIR, HDF5_DIR and MPICH_DIR are set inside the docker image
+      FIREDRAKE_CI_TESTS: 1
+      PYOP2_CI_TESTS: 1
+      PETSC_ARCH: ${{ matrix.petsc_arch }}
+      OMP_NUM_THREADS: 1
+      OPENBLAS_NUM_THREADS: 1
+      RDMAV_FORK_SAFE: 1
+    steps:
+      - name: Cleanup
+        if: ${{ always() }}
+        run: rm -rf pip_venv
+
+      - name: Create a venv
+        run: python -m venv pip_venv
+
+      - uses: actions/checkout@v4
+        with:
+          path: pip_venv/src/firedrake
+
+      - name: Pip install
+        run: |
+          source pip_venv/bin/activate
+          cd pip_venv/src
+          export CC="$MPICH_DIR/mpicc"
+          export CXX="$MPICH_DIR/mpicxx"
+          export MPICC="$MPICH_DIR/mpicc"
+          pip install \
+            --log=firedrake-install.log \
+            --no-binary mpi4py,h5py \
+            -v -e './firedrake[test]'
+
+      - name: Add mpiexec to the venv
+        run: |
+          source pip_venv/bin/activate
+          cat << EOF > $VIRTUAL_ENV/bin/mpiexec
+          #!/bin/bash
+          $MPICH_DIR/mpiexec "\$@"
+          EOF
+          chmod +x $VIRTUAL_ENV/bin/mpiexec
+
+      - name: Test Firedrake
+        run: |
+          source pip_venv/bin/activate
+          cd pip_venv/src/firedrake
+          echo OMP_NUM_THREADS is "$OMP_NUM_THREADS"
+          echo OPENBLAS_NUM_THREADS is "$OPENBLAS_NUM_THREADS"
+          pytest -v tests/firedrake/test_0init.py
+          pytest \
+            --durations=200 \
+            --timeout=1800 \
+            --timeout-method=thread \
+            -o faulthandler_timeout=1860 \
+            -n 12 --dist worksteal \
+            --junit-xml=firedrake.xml \
+            -sv tests
+        timeout-minutes: 120
+
+      - name: Publish Test Report
+        uses: mikepenz/action-junit-report@v5.0.0-a02
+        if: ${{ always() && ( github.ref != 'refs/heads/master') }}
+        with:
+          report_paths: '/__w/firedrake/pip_venv/src/firedrake/firedrake.xml'
+          comment: true
+          check_name: "Firedrake ${{ matrix.scalar-type }}"
+          updateComment: true
+          flaky_summary: true
+
+      - name: Cleanup
+        # Belt and braces: clean up before and after the run.
+        if: ${{ always() }}
+        run: rm -rf pip_venv