formatter: move most of template option helper to formatter We want to share this function between formatter and cmdutils. It doesn't belong in templater because it imports knowledge of ui layers that shouldn't be there. We'd prefer cmdutil to layer on the formatter rather than vice-versa. Since the formatter is the handler for -T options for all non-log commands, let's move the helper there. We leave the bits specific to the old --style option behind.

color: copy docstring of label() template function to wrapper Otherwise label() wouldn't be listed in "hg help template" if color extension is enabled.