Add simple Travis CI validation

This makes sure that .patch files apply cleanly

.travis.yml

+language: c
+
+before_install:
+ - echo "$TRAVIS_COMMIT_RANGE"
+ - echo "$TRAVIS_EVENT_TYPE"
+
+install:
+ - "true"
+
+script:
+ - scripts/travis.sh

scripts/travis.sh

+#!/bin/bash
+
+set -e
+
+case "X$TRAVIS_EVENT_TYPE" in
+    Xpull_request)
+    ;;
+
+    Xpush)
+    ;;
+
+    X*)
+        echo "INFO: not a PR; ignoring"
+        exit 0
+        ;;
+
+    X)
+        echo "ERROR: TRAVIS_EVENT_TYPE not set"
+        exit 1
+        ;;
+esac
+
+if [ -z "$TRAVIS_COMMIT_RANGE" ]; then
+    echo "ERROR: TRAVIS_COMMIT_RANGE not set"
+    exit 1
+fi
+
+CHANGED_FILES=($(git diff --name-only $TRAVIS_COMMIT_RANGE))
+
+
+for FN in "${CHANGED_FILES[@]}"; do
+    if [ ! -f "$FN" ]; then
+        echo "ignoring $FN (not a file (anymore))"
+        continue
+    fi   
+    
+    if [[ "$FN" =~ ^patches/(.*)[.]patch$ ]]; then
+        echo "--------------------------------------------------------------------------------"
+        echo "detected patch file '$FN'"
+        if [[ "$FN" =~ ^patches/([A-Za-z0-9-]+)-([0-9.]+)[.]patch$ ]]; then
+            PKGN="${BASH_REMATCH[1]}"
+            PKGV="${BASH_REMATCH[2]}"
+
+            echo "Patch filename looks valid (name = '$PKGN', version = '$PKGV')"
+
+            rm -rf travis.tmp/
+            mkdir -p travis.tmp/
+            pushd travis.tmp/
+            echo "...downloading original tar-ball (w/o revised .cabal file)..."
+            wget --no-verbose "https://hackage.haskell.org/package/$PKGN-$PKGV.tar.gz"
+            echo "...unpacking..."
+            tar -xf "$PKGN-$PKGV.tar.gz"
+            cd "$PKGN-$PKGV/"
+            echo "...applying patch..."
+            patch -p1 -i "../../$FN"
+
+            echo "Patch could be applied succesfully!"
+            
+            popd
+        else
+            echo "invalid package-id"
+            exit 1
+        fi
+        echo "================================================================================"
+    else
+        echo "ignoring $FN"
+        continue
+    fi
+done
+
+
+echo DONE