ci: run Codecov for commits to main (#1751)

.github/workflows/coverage.yml

@@ -0,0 +1,72 @@
+name: Codecov
+
+on:
+  push:
+    branches:
+      - main
+    paths-ignore:
+      - README*.md
+      - VERSION_INFO
+      - .ci/*
+      - .readthedocs.yml
+      - include/*
+      - src/*
+      - docs-src/*
+      - docs-img/*
+      - docs-jupyter/*
+      - docs-doxygen/*
+      - docs-sphinx/*
+      - studies/*
+
+  workflow_dispatch:
+
+concurrency:
+  group: 'coverage-${{ github.head_ref || github.run_id }}'
+  cancel-in-progress: true
+
+jobs:
+  coverage:
+    runs-on: ubuntu-20.04
+
+    env:
+      PIP_ONLY_BINARY: cmake
+      PYTHON_VERSION: "3.10"
+
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          submodules: true
+
+      - name: Setup ccache
+        uses: hendrikmuhs/[email protected]
+        with:
+          # Maybe share these across workflows?
+          key: >-
+            ${{ github.job }}
+
+      - name: Use ccache
+        run: |
+          echo "/usr/lib/ccache" >> $GITHUB_PATH
+          echo "/usr/local/opt/ccache/libexec" >> $GITHUB_PATH
+
+      - name: 'Python ${{ env.PYTHON_VERSION }}'
+        uses: actions/setup-python@v4
+        with:
+          python-version: '${{ env.PYTHON_VERSION }}'
+
+      - name: Install NumPy
+        run: python -m pip install numpy
+
+      - name: Build
+        run: 'python -m pip install -v .[test,dev]'
+
+      - name: Print versions
+        run: python -m pip list
+
+      - name: Test
+        run: >-
+          python -m pytest -vv -rs tests --cov=awkward --cov-report=term
+          --cov-report=xml
+
+      - name: Upload Codecov results
+        uses: codecov/codecov-action@v3