Automatically find the build configuration file

Automatically find and use a `build-configs.yaml` or `build.yaml` if it
exists.

The `--config-file` option is still available if a custom filename needs
to be used, and it's currently used when running snapshot tests.

src/Command/FindBuildConfigurationFileCommand.php

@@ -0,0 +1,43 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Command;
+
+use Symfony\Component\Filesystem\Filesystem;
+
+final class FindBuildConfigurationFileCommand
+{
+    /**
+     * Supported build configuration file names.
+     */
+    private static $configFiles = [
+        'build-configs.yaml',
+        'build.yaml',
+    ];
+
+    public function __construct(private Filesystem $filesystem)
+    {
+    }
+
+    public function execute(string|null $configFile = null, \Closure $next)
+    {
+        if ($configFile !== null) {
+            if (!$this->filesystem->exists($configFile)) {
+                throw new \RuntimeException(sprintf('%s not found', $configFile));
+            }
+
+            return $next($configFile);
+        }
+
+        // Search for a configuration file in the order of the filenames within
+        // the array and continue if one exists.
+        foreach (self::$configFiles as $i) {
+            if ($this->filesystem->exists($i)) {
+                return $next($i);
+            }
+        }
+
+        throw new \RuntimeException("No configuration file found");
+    }
+}

src/Console/Command/GenerateCommand.php

@@ -6,6 +6,7 @@ namespace App\Console\Command;
 
 use App\Command\CreateFinalConfigurationDataCommand;
 use App\Command\CreateListOfFilesToGenerateCommand;
+use App\Command\FindBuildConfigurationFileCommand;
 use App\Command\GenerateConfigurationFilesCommand;
 use App\Command\ValidateConfigurationDataCommand;
 use App\DataTransferObject\ConfigDto;
@@ -67,6 +68,7 @@ class GenerateCommand extends Command
         $isDryRun = $input->getOption(name: 'dry-run');
 
         $pipelines = [
+            new FindBuildConfigurationFileCommand($this->filesystem),
             new CreateFinalConfigurationDataCommand(),
             new ValidateConfigurationDataCommand(),
             new CreateListOfFilesToGenerateCommand(),