Fix handling of branches with slashes, fixes #1748

src/Composer/Package/Loader/RootPackageLoader.php

@@ -183,7 +183,7 @@ class RootPackageLoader extends ArrayLoader
 
             // find current branch and collect all branch names
             foreach ($this->process->splitLines($output) as $branch) {
-                if ($branch && preg_match('{^(?:\* ) *(?:[^/ ]+?/)?(\S+|\(no branch\)) *([a-f0-9]+) .*$}', $branch, $match)) {
+                if ($branch && preg_match('{^(?:\* ) *(\S+|\(no branch\)) *([a-f0-9]+) .*$}', $branch, $match)) {
                     if ($match[1] === '(no branch)') {
                         $version = 'dev-'.$match[2];
                         $isFeatureBranch = true;
@@ -197,7 +197,7 @@ class RootPackageLoader extends ArrayLoader
                 }
 
                 if ($branch && !preg_match('{^ *[^/]+/HEAD }', $branch)) {
-                    if (preg_match('{^(?:\* )? *(?:[^/ ]+?/)?(\S+) *([a-f0-9]+) .*$}', $branch, $match)) {
+                    if (preg_match('{^(?:\* )? *(\S+) *([a-f0-9]+) .*$}', $branch, $match)) {
                         $branches[] = $match[1];
                     }
                 }