By overriding ui.write(), ui.write_err(), ui.popbuffer(), and ui.label(),
the color extension can avoid parsing command output and simply colorize
output based on labels.
As before, the color extension provides a list of default colors for
core commands/labels. Other extensions can provide their own defaults by
specifying a colortable dict (similar to cmdtable).
In this process, --color is promoted to a global option and the deprecated
--no-color option is removed.
This fixes issue 1569. hg churn <path> now returns only the number
of lines changed in the path, if the path is specified by filtering
files through a match filter at the changeset level. test-churn
has been updated to take care of this issue.
