Don't generate files if the --dry-run option is set

* Add the --dry-run option.
* Add a warning if --dry-run is used saying no files have been
  generated.

src/Action/GenerateConfigurationFiles.php

@@ -16,6 +16,7 @@ final class GenerateConfigurationFiles
         private Filesystem $filesystem,
         private Environment $twig,
         private string $outputDir,
+        private bool $isDryRun = false,
     ) {
     }
 
@@ -28,7 +29,10 @@ final class GenerateConfigurationFiles
          */
         [$configurationData, $configurationDataDto, $filesToGenerate] = $filesToGenerateAndConfigurationData;
 
-        $filesToGenerate->each(function(TemplateFile $templateFile) use ($configurationData): void {
+        if ($this->isDryRun) {
+            return $next([$configurationDataDto, $filesToGenerate]);
+        }
+
             if ($templateFile->path !== null) {
                 if (!$this->filesystem->exists($templateFile->path)) {
                     $this->filesystem->mkdir("{$this->outputDir}/{$templateFile->path}");

src/Command/GenerateCommand.php

@@ -51,6 +51,11 @@ class GenerateCommand extends Command
                 description: 'The directory to create files in',
                 default: '.',
             )
+            ->addOption(
+                name: 'dry-run',
+                mode: InputOption::VALUE_NONE,
+                description: 'Whether to generate files or not',
+            )
         ;
     }
 
@@ -60,18 +65,17 @@ class GenerateCommand extends Command
 
         $configFile = $input->getOption(name: 'config-file');
         $outputDir = $input->getOption(name: 'output-dir');
+        $isDryRun = $input->getOption(name: 'dry-run');
 
         $pipelines = [
             new CreateFinalConfigurationData(),
-
             new ValidateConfigurationData(),
-
             new CreateListOfFilesToGenerate(),
-
             new GenerateConfigurationFiles(
                 $this->filesystem,
                 $this->twig,
                 $outputDir,
+                $isDryRun,
             ),
         ];
 
@@ -86,6 +90,10 @@ class GenerateCommand extends Command
 
         $io->info("Building configuration for {$configurationData->name}.");
 
+        if ($isDryRun === true) {
+            $io->warning('This is a dry run, no files have been generated.');
+        }
+
         $io->write('Generated files:');
         $io->listing(static::getListOfFiles(filesToGenerate: $generatedFiles)->toArray());