Add attach-binary script

.travis.yml

@@ -18,4 +18,4 @@ script:
 - stack setup
 - stack build
 after_success:
-- echo "success"
+- sh travis/attach-binary.sh

travis/attach-binary.sh

@@ -0,0 +1,22 @@
+set -o errexit -o verbose
+
+if test ! "$TRAVIS_TAG"
+then
+  echo 'This is not a release build.'
+elif test ! "$GITHUB_TOKEN"
+then
+  echo 'The GITHUB_TOKEN environment variable is not set!'
+  exit 1
+else
+  echo "Attaching binary for $TRAVIS_OS_NAME to $TRAVIS_TAG..."
+  OWNER="$(echo "$TRAVIS_REPO_SLUG" | cut -f1 -d/)"
+  REPO="$(echo "$TRAVIS_REPO_SLUG" | cut -f2 -d/)"
+  BIN="$(stack path --local-install-root)/bin/$REPO"
+  BUNDLE_NAME="$REPO-$TRAVIS_TAG-$TRAVIS_OS_NAME.tar.gz"
+  cp "$BIN" "./$REPO"
+  chmod +x "./$REPO"
+  tar -czf "$BUNDLE_NAME" "$REPO"
+  echo "SHA256:"
+  shasum -a 256 "$BUNDLE_NAME"
+  ghr -t "$GITHUB_TOKEN" -u "$OWNER" -r "$REPO" --replace "$(git describe --tags)" "$BUNDLE_NAME"
+fi