Add pcre type.

pre_commit/languages/pcre.py

@@ -0,0 +1,27 @@
+from __future__ import unicode_literals
+
+from pre_commit.languages.helpers import file_args_to_stdin
+from pre_commit.util import shell_escape
+
+
+ENVIRONMENT_DIR = None
+
+
+def install_environment(repo_cmd_runner, version='default'):
+    """Installation for pcre type is a noop."""
+    raise AssertionError('Cannot install pcre repo.')
+
+
+def run_hook(repo_cmd_runner, hook, file_args):
+    # For PCRE the entry is the regular expression to match
+    return repo_cmd_runner.run(
+        [
+            'xargs', 'sh', '-c',
+            # Grep usually returns 0 for matches, and nonzero for non-matches
+            # so we flip it here.
+            '! grep -H -n -P {0} $@'.format(shell_escape(hook['entry'])),
+            '--',
+        ],
+        stdin=file_args_to_stdin(file_args),
+        retcode=None,
+    )