annotate: rename {line_number} to {lineno} (BC)
I think {lineno} looks more like a common template keyword. It isn't called
a {line} to avoid conflicts with the element name of {lines} and the
{_|splitlines} filter.
https://www.mercurial-scm.org/wiki/GenericTemplatingPlan#Dictionary
resolve: rename {status} to {mergestatus} to not shadow change status (BC)
This is a part of the name unification. I think it's somewhat useful to
provide a combined view of change/merge statuses.
https://www.mercurial-scm.org/wiki/GenericTemplatingPlan#Dictionary