what about an additional header that will give a mercurial error number that the
client would know about:
HTTP/1.1 200 Script output follows
Date: Sun, 14 Jan 2007 23:22:30 GMT
Server: Apache
X-Mercurial-ErrorCode: 42
Transfer-Encoding: chunked
Content-Type: text/html; charset=ANSI_X3.4-1968
...