travis: build xmonad from HEAD

.travis.yml

@@ -31,6 +31,9 @@ before_install:
  - export PATH=/opt/ghc/$GHCVER/bin:/opt/cabal/$CABALVER/bin:$PATH
 
 install:
+ # build xmonad from HEAD
+ - git clone https://github.com/xmonad/xmonad.git
+
  - cabal --version
  - echo "$(ghc --version) [$(ghc --print-project-git-commit-id 2> /dev/null || echo '?')]"
  - if [ -f $HOME/.cabal/packages/hackage.haskell.org/00-index.tar.gz ];
@@ -66,6 +69,8 @@ install:
       cp -a $HOME/.cabal/lib $HOME/.cabal/share $HOME/.cabal/bin installplan.txt $HOME/.cabsnap/;
    fi
 
+ - cabal install xmonad/
+
 # Here starts the actual work to be performed for the package under test;
 # any command which exits with a non-zero exit code causes the build to fail.
 script: