[PATCH] hgweb: document why we don't allow untrusted settings to control zlib

[Gregory Szorc]

# HG changeset patch
# User Gregory Szorc <gregory.szorc at gmail.com>
# Date 1471318773 25200
#      Mon Aug 15 20:39:33 2016 -0700
# Node ID 4d33314178c961d924de561d725c5febd4cacee0
# Parent  997e8cf4d0a29d28759e38659736cb3d1cf9ef3f
hgweb: document why we don't allow untrusted settings to control zlib

Added comment per discussion on mercurial-devel.

diff --git a/mercurial/hgweb/protocol.py b/mercurial/hgweb/protocol.py
--- a/mercurial/hgweb/protocol.py
+++ b/mercurial/hgweb/protocol.py
@@ -69,16 +69,19 @@ class webproto(wireproto.abstractserverp
     def redirect(self):
         self.oldio = self.ui.fout, self.ui.ferr
         self.ui.ferr = self.ui.fout = stringio()
     def restore(self):
         val = self.ui.fout.getvalue()
         self.ui.ferr, self.ui.fout = self.oldio
         return val
     def groupchunks(self, cg):
+        # Don't allow untrusted settings because disabling compression or
+        # setting a very high compression level could lead to flooding
+        # the server's network or CPU.
         z = zlib.compressobj(self.ui.configint('server', 'zliblevel', -1))
         while True:
             chunk = cg.read(4096)
             if not chunk:
                 break
             yield z.compress(chunk)
         yield z.flush()
     def _client(self):