Store default branch info inside metadata

src/Composer/Package/AliasPackage.php

@@ -392,6 +392,11 @@ class AliasPackage extends BasePackage implements CompletePackageInterface
         return $this->aliasOf->getArchiveExcludes();
     }
 
+    public function isDefaultBranch()
+    {
+        return $this->aliasOf->isDefaultBranch();
+    }
+
     public function isAbandoned()
     {
         return $this->aliasOf->isAbandoned();

src/Composer/Package/Dumper/ArrayDumper.php

@@ -92,6 +92,10 @@ class ArrayDumper
             $data['time'] = $package->getReleaseDate()->format(DATE_RFC3339);
         }
 
+        if ($package->isDefaultBranch()) {
+            $data['default_branch'] = true;
+        }
+
         $data = $this->dumpValues($package, $keys, $data);
 
         if ($package instanceof CompletePackageInterface) {

src/Composer/Package/Loader/ArrayLoader.php

@@ -53,6 +53,9 @@ class ArrayLoader implements LoaderInterface
         } else {
             $version = $this->versionParser->normalize($config['version']);
         }
+        if (isset($config['default_branch']) && $config['default_branch'] === true) {
+            $version = '9999999-dev';
+        }
         $package = new $class($config['name'], $version, $config['version']);
         $package->setType(isset($config['type']) ? strtolower($config['type']) : 'library');
 
@@ -75,6 +78,10 @@ class ArrayLoader implements LoaderInterface
             $package->setInstallationSource($config['installation-source']);
         }
 
+        if (isset($config['default_branch']) && $config['default_branch'] === true) {
+            $package->setIsDefaultBranch(true);
+        }
+
         if (isset($config['source'])) {
             if (!isset($config['source']['type']) || !isset($config['source']['url']) || !isset($config['source']['reference'])) {
                 throw new \UnexpectedValueException(sprintf(

src/Composer/Package/Package.php

@@ -58,6 +58,7 @@ class Package extends BasePackage
     protected $devAutoload = array();
     protected $includePaths = array();
     protected $archiveExcludes = array();
+    protected $isDefaultBranch = false;
 
     /**
      * Creates a new in memory package.
@@ -569,6 +570,22 @@ class Package extends BasePackage
         return $this->archiveExcludes;
     }
 
+    /**
+     * @param bool $defaultBranch
+     */
+    public function setIsDefaultBranch($defaultBranch)
+    {
+        $this->isDefaultBranch = $defaultBranch;
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    public function isDefaultBranch()
+    {
+        return $this->isDefaultBranch;
+    }
+
     /**
      * Replaces current version and pretty version with passed values.
      * It also sets stability.

src/Composer/Package/PackageInterface.php

@@ -352,6 +352,11 @@ interface PackageInterface
      */
     public function getArchiveExcludes();
 
+    /**
+     * @return bool
+     */
+    public function isDefaultBranch();
+
     /**
      * Returns a list of options to download package dist files
      *

src/Composer/Repository/VcsRepository.php

@@ -149,8 +149,10 @@ class VcsRepository extends ArrayRepository implements ConfigurableRepositoryInt
             $this->loader = new ArrayLoader($this->versionParser);
         }
 
+        $hasRootIdentifierComposerJson = false;
         try {
-            if ($driver->hasComposerFile($driver->getRootIdentifier())) {
+            $hasRootIdentifierComposerJson = $driver->hasComposerFile($driver->getRootIdentifier());
+            if ($hasRootIdentifierComposerJson) {
                 $data = $driver->getComposerInformation($driver->getRootIdentifier());
                 $this->packageName = !empty($data['name']) ? $data['name'] : null;
             }
@@ -211,6 +213,9 @@ class VcsRepository extends ArrayRepository implements ConfigurableRepositoryInt
                 $data['version'] = preg_replace('{[.-]?dev$}i', '', $data['version']);
                 $data['version_normalized'] = preg_replace('{(^dev-|[.-]?dev$)}i', '', $data['version_normalized']);
 
+                // make sure tag do not contain the default_branch marker
+                unset($data['default_branch']);
+
                 // broken package, version doesn't match tag
                 if ($data['version_normalized'] !== $parsedTag) {
                     if ($isVeryVerbose) {
@@ -251,6 +256,11 @@ class VcsRepository extends ArrayRepository implements ConfigurableRepositoryInt
         }
 
         $branches = $driver->getBranches();
+        // make sure the root identifier branch gets loaded first
+        if ($hasRootIdentifierComposerJson && isset($branches[$driver->getRootIdentifier()])) {
+            $branches = array($driver->getRootIdentifier() => $branches[$driver->getRootIdentifier()]) + $branches;
+        }
+
         foreach ($branches as $branch => $identifier) {
             $msg = 'Reading composer.json of <info>' . ($this->packageName ?: $this->url) . '</info> (<comment>' . $branch . '</comment>)';
             if ($isVeryVerbose) {
@@ -280,6 +290,9 @@ class VcsRepository extends ArrayRepository implements ConfigurableRepositoryInt
                 $prefix = substr($branch, 0, 1) === 'v' ? 'v' : '';
                 $version = $prefix . preg_replace('{(\.9{7})+}', '.x', $parsedBranch);
             }
+            if ($driver->getRootIdentifier() === $branch) {
+                $parsedBranch = '9999999-dev';
+            }
 
             $cachedPackage = $this->getCachedPackageVersion($version, $identifier, $isVerbose, $isVeryVerbose);
             if ($cachedPackage) {
@@ -305,6 +318,11 @@ class VcsRepository extends ArrayRepository implements ConfigurableRepositoryInt
                 $data['version'] = $version;
                 $data['version_normalized'] = $parsedBranch;
 
+                unset($data['default_branch']);
+                if ($driver->getRootIdentifier() === $branch) {
+                    $data['default_branch'] = true;
+                }
+
                 if ($isVeryVerbose) {
                     $this->io->writeError('Importing branch '.$branch.' ('.$data['version'].')');
                 }