Removed dev-master as default version for versionless artifact

src/Composer/Repository/ArtifactRepository.php

@@ -94,10 +94,6 @@ class ArtifactRepository extends ArrayRepository
             'shasum' => sha1_file($file->getRealPath())
         );
 
-        if(empty($package['version'])) {
-            $package['version'] = 'dev-master';
-        }
-
         $package = $this->loader->load($package);
 
         return $package;

tests/Composer/Test/Repository/ArtifactRepositoryTest.php

@@ -24,8 +24,6 @@ class ArtifactRepositoryTest extends TestCase
         $expectedPackages = array(
             'vendor0/package0-0.0.1',
             'composer/composer-1.0.0-alpha6',
-            'composer/composer-dev-master',
-            'composer/composer-1.0.x-dev',
             'vendor1/package2-4.3.2',
         );