Github Actions basic setup

.github/workflows/covenant.yml

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+name: covenant
+
+on:
+  pull_request:
+  push:
+
+jobs:
+  generate-matrix:
+    name: "Generate matrix from cabal"
+    outputs:
+      matrix: ${{ steps.set-matrix.outputs.matrix }}
+    runs-on: ubuntu-latest
+    steps:
+      - name: Extract the tested GHC versions
+        id: set-matrix
+        uses: kleidukos/get-tested@v0.1.7.1
+        with:
+          cabal-file: covenant.cabal
+          ubuntu-version: "latest"
+          macos-version: "latest"
+          windows-version: "latest"
+          version: 0.1.7.1
+  tests:
+    name: ${{ matrix.ghc }} on ${{ matrix.os }}
+    needs: generate-matrix
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix: ${{ fromJSON(needs.generate-matrix.outputs.matrix) }}
+    steps:
+      - name: Checkout base repo
+        uses: actions/checkout@v3
+      - name: Set up Haskell
+        id: setup-haskell
+        uses: haskell/actions/setup@v2
+        with:
+          ghc-version: ${{ matrix.ghc }}
+          cabal-version: latest
+      - name: Freeze
+        run: cabal freeze
+      - name: Cache
+        uses: actions/cache@v3.3.1
+        with:
+          path: ${{ steps.setup-haskell.outputs.cabal-store }}
+          key: ${{ runner.os}}-${{ matrix.ghc }}-${{ hashFiles('cabal.project.freeze') }}
+          restore-keys: ${{ runner.os }}-${{ matrix.ghc }}-
+      - name: Build
+        run: cabal build