dirstate: ignore sub-second component when either is zero in mtime...
dirstate: ignore sub-second component when either is zero in mtime
When comparing mtimes for equality.
Some APIs simply return zero when more precision is not available.
When comparing values from different sources, if only one is truncated in
that way, doing a simple comparison would cause many false negatives.
Differential Revision:
https://phab.mercurial-scm.org/D11701
