patch: enable diff.tab markup for the color extension
The following patch splits up changed lines along tabs (using
re.findall), and gives them a "diff.tab" label. This can be used by
the color extension for colorising tabs, like it does right now with
trailing whitespace.
I also provide corresponding tests.
To run the tests, do:
cd tests/
python run-tests.py
See http://mercurial.selenic.com/wiki/WritingTests for
more information on writing tests.