fix(cli-create): fix scoped creation

This one works as it should:
yarn create @scope/name => @scope/create-name

There were problems when name was omitted:

Before:
yarn create @scope => create-
yarn create @scope/ => @scope/create-

After:
yarn create @scope => @scope/create
yarn create @scope/ => @scope/create

Fixes #6233

src/cli/commands/create.js

@@ -16,17 +16,50 @@ export function hasWrapper(commander: Object, args: Array<string>): boolean {
  return true;
 }
 
+const coerceName = (name = '') => (name === '' ? 'create' : `create-${name}`);
+const coerceScope = (scope = '') => (scope === '@' ? undefined : scope);
+const coerceFullName = (scope, name) => [coerceScope(scope), coerceName(name)].filter(Boolean).join('/');
+
+/**
+ * # Tests
+ *
+ * ## basic
+ * parseBuilderName('name').packageName === 'create-name'
+ * parseBuilderName('@scope/name').packageName === '@scope/create-name'
+ *
+ * ## not adding "-" if name is empty
+ * parseBuilderName('@scope/').packageName === '@scope/create'
+ * parseBuilderName('@scope').packageName === '@scope/create'
+ *
+ * ## edge cases
+ * parseBuilderName('@/name').packageName === 'create-name'
+ * parseBuilderName('/name').packageName === 'create-name'
+ * parseBuilderName('@/').packageName === 'create'
+ */
+const parseBuilderName = str => {
+ const parts = str.split('/');
+ if (parts.length === 1 && !str.includes('@')) {
+ return {
+ packageName: coerceName(str),
+ packageDir: '',
+ commandName: coerceName(str),
+ };
+ }
+ return {
+ packageName: coerceFullName(parts[0], parts[1]),
+ packageDir: coerceScope(parts[0]),
+ commandName: coerceName(parts[1]),
+ };
+};
+
 export async function run(config: Config, reporter: Reporter, flags: Object, args: Array<string>): Promise<void> {
  const [builderName, ...rest] = args;
 
  if (!builderName) {
  throw new MessageError(reporter.lang('invalidPackageName'));
  }
 
- const packageName = builderName.replace(/^(@[^\/]+\/)?/, '$1create-');
- const packageDir = packageName.replace(/^(?:(@[^\/]+)\/)?.*/, '$1');
- const commandName = packageName.replace(/^@[^\/]+\//, '');
-
+ const {packageName, packageDir, commandName} = parseBuilderName(builderName);
  await runGlobal(config, reporter, {}, ['add', packageName]);
 
  const binFolder = await getBinFolder(config, {});