Fix #9: Add CI (#11)

* Add CI

* Try setup-agda@main, add more Agda versions
   We should use @latest, not @main, but see wenkokke/setup-agda#205

* Mention CI in README.md

* README: fix wording

Author: andreasabel

.github/workflows/agda-ci.yml

@@ -0,0 +1,62 @@
+name: agda-ci
+
+on:
+  push:         { branches: [master] }
+  pull_request: { branches: [master] }
+  workflow_dispatch:
+
+jobs:
+  build:
+    name: Agda ${{ matrix.agda }} on ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
+
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest]
+        agda:
+          ## we need std-lib >= 1.0 which is not compatible with Agda 2.5.*
+          # - 2.6.0.1  ## build error: Ambiguous module Wk
+          - 2.6.1.3
+          - 2.6.2.2
+          - 2.6.3
+          - 2.6.4
+          - 2.6.4.1
+
+    steps:
+
+      # Checkout to $HOME empties $HOME so we have to do it before we put stuff there.
+      - uses: actions/checkout@v4
+
+      - name: Setup Agda
+        uses: wenkokke/setup-agda@main
+          # 2024-01-24 we should use @latest but this does not have 2.6.4.1 yet
+          # https://github.com/wenkokke/setup-agda/issues/205
+        id:   setup
+        with:
+          agda-version: ${{ matrix.agda }}
+          agda-stdlib-version: recommended
+
+      - name: Restore cache
+        uses: actions/cache/restore@v4
+        id:   cache
+        env:
+          key: ${{ runner.os }}-agda-${{ steps.setup.outputs.agda-version }}
+        with:
+          key:          ${{ env.key }}-commit-${{ github.sha }}
+          restore-keys: ${{ env.key }}-
+          path: |
+            _build
+            ~/.agda/libraries.d
+
+      - name: Build
+        run: make
+
+      - name: Save cache
+        if: always()
+        uses: actions/cache/save@v4
+        with:
+          key: ${{ steps.cache.outputs.cache-primary-key }}
+          path: |
+            _build
+            ~/.agda/libraries.d

README.md

@@ -27,4 +27,7 @@ Since then, the project has been extended in the following ways:
 ### Dependencies ###
 
 This project is written in Agda.
-It has been tested to be working with Agda version 2.6.2 and its standard library.
+It is compatible with Agda version ≥ 2.6.1 and the
+[matching standard library](https://wiki.portal.chalmers.se/agda/Libraries/StandardLibrary).
+The full list of tested Agda versions can be found in the
+[continuous integration script](.github/workflows/agda-ci.yml).