Export hardcoded VERSION variable

For a less bold approach, the exported VERSION variable is now
hardcoded. Meanwhile, the `scripts/tag` script was improved to
ensure that all versions match.

See #800 (comment).

Resolves #747 and #799.

scripts/tag

@@ -1,10 +1,21 @@
 #!/usr/bin/env bash
 
+abort() {
+  echo "ERROR: $1"
+  exit 1
+}
+
 PACKAGE_VERSION=$(node -p "require('./package.json').version")
+PACKAGE_LOCK_VERSION=$(node -p "require('./package-lock.json').version")
+EXPORTED_VERSION=$(grep -oP "(?<=const VERSION = \").*(?=\";)" ./src/luxon.js)
 
-if [ $(git tag -l "$PACKAGE_VERSION") ]; then
-  echo "tag already exists"
-else
-  git tag $PACKAGE_VERSION
-  git push origin master $PACKAGE_VERSION 
+if [ $PACKAGE_VERSION != $PACKAGE_LOCK_VERSION ]; then
+  abort "package-lock.json's version differs from package.json's"
+elif [ $PACKAGE_VERSION != $EXPORTED_VERSION ]; then
+  abort "exported version differs from package.json's"
+elif [ $(git tag -l "$PACKAGE_VERSION") ]; then
+  abort "tag already exists"
 fi
+
+git tag $PACKAGE_VERSION
+git push origin master $PACKAGE_VERSION

src/luxon.js

@@ -9,7 +9,10 @@ import InvalidZone from "./zones/invalidZone.js";
 import LocalZone from "./zones/localZone.js";
 import Settings from "./settings.js";
 
+const VERSION = "1.25.0";
+
 export {
+  VERSION,
   DateTime,
   Duration,
   Interval,