contrib/hgweb.wsgi

mdiff: convert a few block definitions from lists to tuples

These were flagged by adding type hints.  Some places were using a tuple of 4
ints to define a block, and others were using a list of 4.  A tuple is better
for typing, because we can define the length and the type of each entry.  One of
the places had to redefine the tuple, since writing to a tuple at an index isn't
supported.

This change spills out into the tests, and archeology says it was added to the
repo in this state.  There was no reason given for the divergence, and I suspect
it wasn't intentional.

It looks like `splitblock()` is completely unused in the codebase.

# An example WSGI for use with mod_wsgi, edit as necessary
# See https://mercurial-scm.org/wiki/modwsgi for more information

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

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

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