Downgrade .gitlab-ci.yml to support old CI

This commit removes the 'cache:key:files' directive because our CI's
gitlab is currently too old to support it.

.gitlab-ci.yml

@@ -17,28 +17,20 @@ stages:
 
 stack:
   stage: stack
-  cache:
-    key:
-      files:
-        - stack.yaml
+  cache: 
+    key: stack.yaml
     paths:
       - .stack-root/
       - .stack-work/
-      - dist-newstyle/
-      - .cabal/
   script:
     - echo "Building the project from '$CI_PROJECT_DIR'"
     - nix-shell --run "stack build --no-terminal --fast --dry-run"
 
 cabal:
   stage: cabal
-  cache:
-    key:
-      files:
-        - cabal.project
+  cache: 
+    key: cabal.project
     paths:
-      - .stack-root/
-      - .stack-work/
       - dist-newstyle/
       - .cabal/
     policy: pull-push
@@ -49,12 +41,8 @@ cabal:
 test:
   stage: test
   cache:
-    key:
-      files:
-        - gargantext.cabal
+    key: cabal.project
     paths:
-      - .stack-root/
-      - .stack-work/
       - dist-newstyle/
       - .cabal/
     policy: pull
@@ -64,20 +52,21 @@ test:
 docs:
   stage: docs
   cache:
+    key: stack.yaml
     paths:
       - .stack-root/
       - .stack-work/
-      - dist-newstyle/
-      - .cabal/
-      - target
     policy: pull
   script:
     - nix-shell --run "stack build --no-terminal --haddock --no-haddock-deps --fast --dry-run"
     - cp -R "$(stack path --local-install-root)"/doc ./output
-  rules:
-    - if: '$CI_MERGE_REQUEST_IID' # Run job on Merge Requests
+  # FIXME(adinapoli) Currently Gitlab 11.x doesn't support the 'rules' keyword.
+  # rules:
+  # - if: '$CI_MERGE_REQUEST_IID' # Run job on Merge Requests
+  only:
+    - merge_requests
   artifacts:
     paths:
       - ./output
     expire_in: 1 week
-  allow_failure: true
+  allow_failure: true
\ No newline at end of file