Fix detection of tags when the current tag is not a valid version

src/Composer/Package/Loader/RootPackageLoader.php

@@ -190,7 +190,10 @@ class RootPackageLoader extends ArrayLoader
 
         // try to fetch current version from git tags
         if (0 === $this->process->execute('git describe --exact-match --tags', $output)) {
-            return $this->versionParser->normalize(trim($output));
+            try {
+                return $this->versionParser->normalize(trim($output));
+            } catch (\Exception $e) {
+            }
         }
 
         // try to fetch current version from git branch

tests/Composer/Test/Package/Loader/RootPackageLoaderTest.php

@@ -85,6 +85,39 @@ class RootPackageLoaderTest extends \PHPUnit_Framework_TestCase
         $this->assertEquals("2.0.5.0-alpha2", $package->getVersion());
     }
 
+    public function testInvalidTagBecomesVersion()
+    {
+        if (!function_exists('proc_open')) {
+            $this->markTestSkipped('proc_open() is not available');
+        }
+
+        $manager = $this->getMockBuilder('\\Composer\\Repository\\RepositoryManager')
+            ->disableOriginalConstructor()
+            ->getMock();
+
+        $self = $this;
+
+        /* Can do away with this mock object when https://github.com/sebastianbergmann/phpunit-mock-objects/issues/81 is fixed */
+        $processExecutor = new ProcessExecutorMock(function($command, &$output = null, $cwd = null) use ($self) {
+            if ('git describe --exact-match --tags' === $command) {
+                $output = "foo-bar";
+
+                return 0;
+            }
+
+            $output = "* foo 03a15d220da53c52eddd5f32ffca64a7b3801bea Commit message\n";
+
+            return 0;
+        });
+
+        $config = new Config;
+        $config->merge(array('repositories' => array('packagist' => false)));
+        $loader = new RootPackageLoader($manager, $config, null, $processExecutor);
+        $package = $loader->load(array());
+
+        $this->assertEquals("dev-foo", $package->getVersion());
+    }
+
     protected function loadPackage($data)
     {
         $manager = $this->getMockBuilder('\\Composer\\Repository\\RepositoryManager')