contrib/hgweb.wsgi

transaction: add a validation stage

The 'transaction' object can now be fed a 'validator' function. This function
will be run right before the transaction is closed to validate its content. The
target usage is hooks. The validation function is expected to raise an exception
when it wants to abort the transaction.

This only introduce the idea with a default no-op validator. Actual usage is in
the next changeset.

# An example WSGI for use with mod_wsgi, edit as necessary
# See http://mercurial.selenic.com/wiki/modwsgi for more information

# Path to repo or hgweb config to serve (see 'hg help hgweb')
config = "/path/to/repo/or/config"

# Uncomment and adjust if Mercurial is not installed system-wide
# (consult "installed modules" path from 'hg debuginstall'):
#import sys; sys.path.insert(0, "/path/to/python/lib")

# Uncomment to send python tracebacks to the browser if an error occurs:
#import cgitb; cgitb.enable()

# enable demandloading to reduce startup time
from mercurial import demandimport; demandimport.enable()

from mercurial.hgweb import hgweb
application = hgweb(config)