dirstate-tree: Refactor DirstateMap::drop_file to be recursive...
dirstate-tree: Refactor DirstateMap::drop_file to be recursive
It should behave the same as before. This will enable the next changeset
to run code on the way "down" (in order to removing newly-empty nodes).
Differential Revision:
https://phab.mercurial-scm.org/D10705