No need to create hg working copies just to parse tags/branches

src/Composer/Repository/Vcs/HgDriver.php

@@ -49,14 +49,14 @@ class HgDriver extends VcsDriver
 
             // update the repo if it is a valid hg repository
             if (is_dir($this->repoDir) && 0 === $this->process->execute('hg summary', $output, $this->repoDir)) {
-                if (0 !== $this->process->execute('hg pull -u', $output, $this->repoDir)) {
+                if (0 !== $this->process->execute('hg pull', $output, $this->repoDir)) {
                     $this->io->write('<error>Failed to update '.$this->url.', package information from this repository may be outdated ('.$this->process->getErrorOutput().')</error>');
                 }
             } else {
                 // clean up directory and do a fresh clone into it
                 $fs->removeDirectory($this->repoDir);
 
-                if (0 !== $this->process->execute(sprintf('hg clone %s %s', escapeshellarg($this->url), escapeshellarg($this->repoDir)), $output, $cacheDir)) {
+                if (0 !== $this->process->execute(sprintf('hg clone --noupdate %s %s', escapeshellarg($this->url), escapeshellarg($this->repoDir)), $output, $cacheDir)) {
                     $output = $this->process->getErrorOutput();
 
                     if (0 !== $this->process->execute('hg --version', $ignoredOutput)) {