Fix generate:migration command for extensions

Apparently, this code was from back when we had a special "extensions"
directory for Composer packages marked as Flarum extensions.

While we're at it, we now inject the Paths instance instead of using one
of the global helpers (which I am trying to get rid of).

Refs #2055.

src/Database/MigrationCreator.php

@@ -9,7 +9,7 @@
 
 namespace Flarum\Database;
 
-use Flarum\Extension\Extension;
+use Flarum\Foundation\Paths;
 use Illuminate\Filesystem\Filesystem;
 
 class MigrationCreator
@@ -22,27 +22,28 @@ class MigrationCreator
     protected $files;
 
     /**
-     * @var string
+     * @var Paths
      */
-    protected $publicPath;
+    protected $paths;
 
     /**
      * Create a new migrator instance.
      *
      * @param Filesystem $files
-     * @param string $publicPath
+     * @param Paths $paths
      */
-    public function __construct(Filesystem $files, $publicPath)
+    public function __construct(Filesystem $files, Paths $paths)
     {
         $this->files = $files;
-        $this->publicPath = $publicPath;
+        $this->paths = $paths;
+        #
     }
 
     /**
      * Create a new migration for the given extension.
      *
      * @param string $name
-     * @param Extension $extension
+     * @param string $extension
      * @param string $table
      * @param bool $create
      * @return string
@@ -105,9 +106,11 @@ protected function populateStub($stub, $table)
      */
     protected function getMigrationPath($extension)
     {
-        $parent = $extension ? public_path('extensions/'.$extension) : __DIR__.'/../..';
-
-        return $parent.'/migrations';
+        if ($extension) {
+            return $this->paths->vendor.'/'.$extension.'/migrations';
+        } else {
+            return __DIR__.'/../../migrations';
+        }
     }
 
     /**

src/Database/MigrationServiceProvider.php

@@ -23,12 +23,5 @@ public function register()
         $this->app->singleton(MigrationRepositoryInterface::class, function ($app) {
             return new DatabaseMigrationRepository($app['flarum.db'], 'migrations');
         });
-
-        $this->app->bind(MigrationCreator::class, function () {
-            return new MigrationCreator(
-                $this->app->make(Filesystem::class),
-                $this->app->make(Paths::class)->base
-            );
-        });
     }
 }