A HTTP client can indicate that it doesn't support (or doesn't want)
persistent connections by sending this header.
This not only makes the server more compliant with the RFC, but also
reduces the run time of test-http-proxy when run with python 2.3 from
~125s to ~5s (it doesn't affect it with python 2.4, which was already
~5s).
First, it changes the server to be almost a generic WSGI server.
Second, it changes request.py to have wsgiapplication and
_wsgirequest. wsgiapplication is a class that creates _wsgirequests
when called by a WSGI compliant server. It needs to know whether
or not it should create hgwebdir or hgweb requests.
Lastly, wsgicgi.py is added, and the CGI scripts are altered to
use it to launch wsgiapplications in a WSGI compliant way.
As a side effect, all the keepalive code has been removed from
request.py. This code needs to be moved so that it is exclusively
in server.py
only "hg serve" affected yet. http server running cgi script will not
use persistent connections. support for fastcgi will help that.
clients that support keepalive can use one tcp connection for all
commands during clone and pull. this makes latency of binary search
during pull much lower over wan.
if server does not know content-length, it will force connection to
close at end. right fix is to use chunked transfer-encoding but this is
easier and does not hurt performance. only command that is affected is
"changegroup" which is always last command during a pull.
