style: always use `x is not None` instead of `not x is None` Differential Revision: https://phab.mercurial-scm.org/D842

templatekw: add new-style template expansion to {manifest} The goal is to allow us to easily access to nested data. The dot operator will be introduced later so we can write '{p1.files}' instead of '{revset("p1()") % "{files}"}' for example. In the example above, 'p1' needs to carry a mapping dict along with its string representation. If it were a list or a dict, it could be wrapped semi-transparently with the _hybrid class, but for non-list/dict types, it would be difficult to proxy all necessary functions to underlying value type because several core operations may conflict with the ones of the underlying value: - hash(value) should be different from hash(wrapped(value)), which means dict[wrapped(value)] would be invalid - 'value == wrapped(value)' would be false, breaks 'ifcontains' - len(wrapped(value)) may be either len(value) or len(iter(wrapped(value))) So the wrapper has no proxy functions and its scope designed to be minimal. It's unwrapped at eval*() functions so we don't have to care for a wrapped object unless it's really needed: # most template functions just call evalfuncarg() unwrapped_value = evalfuncarg(context, mapping, args[n]) # if wrapped value is needed, use evalrawexp() maybe_wrapped_value = evalrawexp(context, mapping, args[n]) Another idea was to wrap every template variable with a tagging class, but which seemed uneasy without a static type checker. This patch updates {manifest} to a mappable as an example.