pretxnchangegroup hook on http server

[Teemu Torma]

I tried installing a pretxnchangegroup hook on a repo served by 
hgweb.cgi to prevent creating new heads on the repo with push -f.  The 
hook uses hg heads to see if more than one head is present.

In local repo test the hook works fine and prevents push creating new 
heads, but with hgweb.cgi the push -f fails to the client 
with "abort: .. does not appear to be an hg repository" and leaves the 
server repository in interrupted transaction state.  After hg recover, 
the push appears to have succeeded and the repository now has two 
heads.

Am I doing something wrong, or missing something?

The server is using recent snapshot (2dc74b630c00) and client is 0.9.2.

Teemu