dirstate-v2: Extend node flags to 16 bits...
dirstate-v2: Extend node flags to 16 bits
Only 7 out of 8 available bits are used right now. Reserve some more.
Future versions of Mercurial may assign meaning to some of these bits,
with the limitation that then-older versions will always reset those bits to
unset when writing nodes.
(A new node is written for any mutation in its subtree, leaving the bytes of
the old node unreachable until the data file is rewritten entirely.)
Differential Revision:
https://phab.mercurial-scm.org/D11661
