Move PrefixedCommandRunner -> Prefix

pre_commit/prefix.py

@@ -0,0 +1,20 @@
+from __future__ import unicode_literals
+
+import os.path
+
+
+class Prefix(object):
+    def __init__(self, prefix_dir):
+        self.prefix_dir = prefix_dir.rstrip(os.sep) + os.sep
+
+    def path(self, *parts):
+        path = os.path.join(self.prefix_dir, *parts)
+        return os.path.normpath(path)
+
+    def exists(self, *parts):
+        return os.path.exists(self.path(*parts))
+
+    def star(self, end):
+        return tuple(
+            path for path in os.listdir(self.prefix_dir) if path.endswith(end)
+        )