Add pcre type.

pre_commit/languages/helpers.py

@@ -1,10 +1,14 @@
 from __future__ import unicode_literals
 
 
+def file_args_to_stdin(file_args):
+    return '\n'.join(list(file_args) + [''])
+
+
 def run_hook(env, hook, file_args):
     return env.run(
         ' '.join(['xargs', hook['entry']] + hook['args']),
-        stdin='\n'.join(list(file_args) + ['']),
+        stdin=file_args_to_stdin(file_args),
         retcode=None,
     )