dirstate-tree: Downgrade `&mut Node` to `&Node` in status and serialization...
dirstate-tree: Downgrade `&mut Node` to `&Node` in status and serialization
Mutable access is not used, and upcoming changes will make it more costly
(with copy-on-write nodes that can be read from disk representation)
Differential Revision:
https://phab.mercurial-scm.org/D10745