Fix release script to fail if not run from trunk (purescript#791)

Author: f-f

release.sh

@@ -6,11 +6,20 @@ set -euo pipefail
 # It will create a tag and push it, which will trigger CI to create a release,
 # build release binaries, push them to the release, and publish a new version on NPM
 
+# Fail if we are not on trunk
+BRANCH=$(git branch --show-current)
+if [ "${BRANCH}" != "master" ]; then
+  echo "Please checkout master branch"
+  exit 1;
+fi
+git pull
+
 NEW_TAG=$(./scripts/get-version)
 
 # Fail if the new tag already exists
+# Note: exit status of the command is the conditional
 if git rev-parse "${NEW_TAG}" >/dev/null 2>&1; then
-  echo "Tag '${NEW_TAG}' already exists, please bump the version in package.yaml";
+  echo "Tag '${NEW_TAG}' already exists, please bump the version in spago.cabal";
   exit 1;
 fi
 
@@ -20,4 +29,4 @@ git tag "${NEW_TAG}"
 
 git push origin "${NEW_TAG}"
 
-echo "Done."
+echo "Done."