contrib/python-hook-examples.py

highlight: fix encoding issues to enable Py3 compatibility

This commit fixes various encoding issues with the `highlight` extension
to enable compatibility with Python 3. Python `.encode()` and `.decode()`
requires the target encoding to be passed as a `str`, so the value of
`mercurial.encoding.encoding` must be converted before passing to the
function. Pygments also assumes the `str` type for values it works with,
so we must perform conversions before and after receiving values from its
APIs.

After applying this patch, `test-highlight.t` passes under Python 3. We
add it to `python3-whitelist` as well.

Tested with Pygments 2.4.2.

Differential Revision: https://phab.mercurial-scm.org/D6832

'''
Examples of useful python hooks for Mercurial.
'''
from __future__ import absolute_import
from mercurial import (
    patch,
    util,
)

def diffstat(ui, repo, **kwargs):
    '''Example usage:

    [hooks]
    commit.diffstat = python:/path/to/this/file.py:diffstat
    changegroup.diffstat = python:/path/to/this/file.py:diffstat
    '''
    if kwargs.get('parent2'):
        return
    node = kwargs['node']
    first = repo[node].p1().node()
    if 'url' in kwargs:
        last = repo.changelog.tip()
    else:
        last = node
    diff = patch.diff(repo, first, last)
    ui.write(patch.diffstat(util.iterlines(diff)))