simplify upgrade generator

cli/cli.mjs

@@ -33,16 +33,10 @@ const __dirname = dirname(__filename);
 const currentNodeVersion = process.versions.node;
 const minimumNodeVersion = packageJson.engines.node;
 
-if (!process.argv.includes('--skip-checks')) {
-  if (
-    !semver.satisfies(currentNodeVersion, minimumNodeVersion) &&
-    // Allow upgrade to be executed using node 16 due to https://github.com/jhipster/generator-jhipster/issues/20349
-    (!process.argv.includes('upgrade') || !semver.satisfies(currentNodeVersion, '^16.0.0'))
-  ) {
-    logger.fatal(
-      `You are running Node version ${currentNodeVersion}\nJHipster requires Node version ${minimumNodeVersion}\nPlease update your version of Node.`,
-    );
-  }
+if (!process.argv.includes('--skip-checks') && !semver.satisfies(currentNodeVersion, minimumNodeVersion)) {
+  logger.fatal(
+    `You are running Node version ${currentNodeVersion}\nJHipster requires Node version ${minimumNodeVersion}\nPlease update your version of Node.`,
+  );
 }
 
 const appFolderOrWorkspaceRoot = existsSync('../node_modules') ? join(process.cwd(), '..') : process.cwd();

generators/upgrade/README.md

@@ -0,0 +1,15 @@
+# upgrade sub-generador
+
+Upgrades the application the a newer generator-jhipster version.
+
+The upgrade process generates 4 commits.
+
+- the reference application
+- a merge commit with unrelated histories
+- the upgrade application
+- a merge commit to apply the upgrade commit to the existing application
+
+## Upgrading from v7
+
+To upgrade to v8 you need to upgrade to v7.9.4 before due to node v18/v20 compatibility.
+If you use blueprint that uses jhipster v7, you need to use [jhipster-migrate](https://github.com/jhipster/generator-jhipster-migrate/).

generators/upgrade/USAGE

@@ -1,12 +1,13 @@
 Description:
-    Updates JHipster version, and upgrades generated application
+    Upgrades generated application
 
 Example:
 
     jhipster upgrade
 
     Assuming you have Git installed, and you run this command in the Git branch you are using for development, JHipster Upgrader will :
     - checkout a "jhipster_upgrade" branch
-    - update generator-jhipster via npm
-    - regenerate your whole application
-    - switch back to your development branch, and start the merge
+    - generate a application upgrade reference
+    - apply the reference point to your application
+    - generate the upgraded application
+    - switch back to your original branch and merge the upgrade branch into it

generators/upgrade/command.ts

@@ -20,16 +20,6 @@ import { JHipsterCommandDefinition } from '../base/api.js';
 
 const command: JHipsterCommandDefinition = {
   options: {
-    targetJhipsterVersion: {
-      name: 'targetVersion',
-      description: 'Upgrade to a specific version instead of the latest',
-      type: String,
-      scope: 'generator',
-    },
-    targetBlueprintVersions: {
-      description: 'Upgrade to specific blueprint versions instead of the latest, e.g. --target-blueprint-versions foo@0.0.1,bar@1.0.2',
-      type: String,
-    },
     silent: {
       description: 'Hides output of the generation process',
       type: Boolean,