Refactor pre_commit.repository and factor out cached-property

pre_commit/meta_hooks/helpers.py

@@ -0,0 +1,10 @@
+import pipes
+import sys
+
+
+def make_meta_entry(modname):
+    """the hook `entry` is passed through `shlex.split()` by the command
+    runner, so to prevent issues with spaces and backslashes (on Windows)
+    it must be quoted here.
+    """
+    return '{} -m {}'.format(pipes.quote(sys.executable), modname)