color: handle 'ui.plain()' directly in mode setup
If 'ui.plain()' is set we should not colorize. We move that logic into the
function that determine and setup the color mode. As all other code respect
the resulting mode this will be equivalent.
#!/bin/sh
HGENCODING=UTF-8
export HGENCODING
echo ".. -*- coding: utf-8 -*-" > gendoc.txt
echo "" >> gendoc.txt
LANGUAGE=$1 python "$TESTDIR/../doc/gendoc.py" >> gendoc.txt 2> /dev/null || exit
echo "checking for parse errors"
python "$TESTDIR/../doc/docchecker" gendoc.txt
python "$TESTDIR/../doc/runrst" html gendoc.txt /dev/null