# HG changeset patch
# User Jun Wu <quark@fb.com>
# Date 2016-06-29 22:53:20
# Node ID 71ed5a3ef8a9ba9499fe7e30b66cddb5f188ca6e
# Parent  7d88fde2309f6abc1ff81a9764122d8c6d35fca7

chgserver: document why we don't merge mtimehash and confighash

People may get confused about chg's mtimehash and confighash design: why two
hashes instead of just one. This patch adds text addressing the concern.

diff --git a/hgext/chgserver.py b/hgext/chgserver.py
--- a/hgext/chgserver.py
+++ b/hgext/chgserver.py
@@ -154,6 +154,10 @@ def _mtimehash(paths):
 
     for chgserver, it is designed that once mtimehash changes, the server is
     considered outdated immediately and should no longer provide service.
+
+    mtimehash is not included in confighash because we only know the paths of
+    extensions after importing them (there is imp.find_module but that faces
+    race conditions). We need to calculate confighash without importing.
     """
     def trystat(path):
         try: