dirstate-v2: Change the representation of negative directory mtime...
dirstate-v2: Change the representation of negative directory mtime
Change it from how I previously thought C’s `timespec` works
to how it actually works.
The previous behavior was also buggy for timestamps strictly before the
epoch but less than one second away from it, because two’s complement
does not distinguish negative zero from positive zero.
Differential Revision:
https://phab.mercurial-scm.org/D11629
