dirstate: reorder "state" checking conditional
This is easier to read and will make this simpler to update in the next
changeset.
Differential Revision: https://phab.mercurial-scm.org/D10975
dirstate-entry: add a `need_delay` method
This abstract the internal processing need for entry that would have an
ambiguous mtime (If I understand things correctly).
Differential Revision: https://phab.mercurial-scm.org/D10974
dirstate-entry: add a `tracked` property
This abstract the individual `state` value and has a clear semantic.
Differential Revision: https://phab.mercurial-scm.org/D10973