Add update-wrapper command + update readme

README.md

@@ -3,13 +3,30 @@
 #### Build Status
 - [![Java CI](https://github.com/grails/grails-wrapper/actions/workflows/gradle.yml/badge.svg?event=push)](https://github.com/grails/grails-wrapper/actions/workflows/gradle.yml)
 
+Update to the latest wrapper release based on Grails version
+---
+
+    ./grailsw update-wrapper
+
 Versions
 ---
 
 | Grails        | Wrapper                                                       |
 |---------------|---------------------------------------------------------------|
 | 5.0.0 - 5.3.3 | [3.0.0.M1](https://github.com/grails/grails-wrapper/releases) |
-| 5.3.4 - 5.3.X | [3.1.0](https://github.com/grails/grails-wrapper/releases)    |
-| 6.x.x         | [4.0.0](https://github.com/grails/grails-wrapper/releases)    |
-| 7.x.x         | [5.0.0](https://github.com/grails/grails-wrapper/releases)    |
+| 5.3.4 - 5.3.X | [3.1.x](https://github.com/grails/grails-wrapper/releases)    |
+| 6.x.x         | [4.0.x](https://github.com/grails/grails-wrapper/releases)    |
+| 7.x.x         | [6.0.x](https://github.com/grails/grails-wrapper/releases)    |
+
+Release Process
+---
+
+- Release new version via GitHub Releases
+- After GitHub action is completed and only after the new release is visible on https://central.sonatype.com/artifact/org.grails/grails7-wrapper/versions
+- Update the branch to trigger gradle.yml to publish the next snapshot which will update the release version on https://repo.grails.org/artifactory/core/org/grails/grails7-wrapper/maven-metadata.xml
+- The release version will be installed locally by grails-wrapper.jar, latest is only used when release is not present
 
+```xml
+    <latest>6.0.1-SNAPSHOT</latest>
+    <release>6.0.0</release>
+```

starter/src/main/java/grails/init/Start.java

@@ -102,9 +102,15 @@ public static void main(String[] args) {
         Authenticator.setDefault(new SystemPropertiesAuthenticator());
 
         try {
-            if (!NO_VERSION_JAR.exists()) {
+            if (!NO_VERSION_JAR.exists() || (args.length > 0 && args[0].trim().equals("update-wrapper"))) {
+                System.out.println("Updating Grails wrapper jar to version: " + getVersion() + " located in: " + NO_VERSION_JAR.getAbsolutePath());
                 updateJar(getVersion());
+                // remove "update-wrapper" command argument
+                if(args.length > 0) {
+                    args[0] = null;
+                }
             }
+
             URLClassLoader child = new URLClassLoader(new URL[]{NO_VERSION_JAR.toURI().toURL()});
             Class<?> classToLoad = Class.forName("grails.init.RunCommand", true, child);
             Method main = classToLoad.getMethod("main", String[].class);