Add CI workflow against xmonad latest commit (xmonad#429)

.github/workflows/tests.yml

@@ -14,18 +14,20 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest]
-        resolver: [lts-16, lts-15, lts-14]
+        resolver: [lts-16, lts-15, lts-14, lts-12]
+        yaml: ['stack.yaml', 'stack-master.yaml']
 
     steps:
       - name: Clone project
         uses: actions/checkout@v2
 
       - name: Cache dependencies
-        uses: actions/cache@v1
+        uses: actions/cache@v2
         with:
           path: ~/.stack
-          key: ${{ runner.os }}-${{ matrix.resolver }}-${{ hashFiles('stack.yaml') }}
+          key: ${{ runner.os }}-${{ matrix.resolver }}-${{ hashFiles(matrix.yaml) }}-${{ hashFiles('xmonad-contrib.cabal') }}
           restore-keys: |
+            ${{ runner.os }}-${{ matrix.resolver }}-${{ hashFiles(matrix.yaml) }}-
             ${{ runner.os }}-${{ matrix.resolver }}-
 
       - name: Build and run tests
@@ -35,4 +37,4 @@ jobs:
             curl -sSL https://get.haskellstack.org/ | sh -s - -f
             sudo apt install -y libasound2 libasound2-dev libxrandr-dev libtinfo-dev
             sudo apt install -y libx11-dev libgmp-dev libxss-dev libxft-dev 
-            stack test --fast --no-terminal --resolver=${{ matrix.resolver }}
+            stack --stack-yaml=${{ matrix.yaml }} test --fast --no-terminal --resolver=${{ matrix.resolver }}

stack-master.yaml

@@ -0,0 +1,11 @@
+# This stack.yaml is used to build xmonad-contrib with master version
+# of xmonad
+
+resolver: lts-15.3
+
+packages:
+- ./
+
+extra-deps:
+- github: xmonad/xmonad
+  commit: master

stack.yaml

@@ -1,4 +1,7 @@
 resolver: lts-15.3
 
+extra-deps:
+- xmonad-0.15
+
 packages:
   - ./