dirstate: Don’t drop unrelated data in DirstateMap::set_entry

For example, copy source are handled separately. Removing it goes through
the `copy_map_remove` method (exposed to Python as `.copymap.pop()`)

Differential Revision: https://phab.mercurial-scm.org/D11488

rust/hg-core/src/dirstate_tree/dirstate_map.rs

@@ -762,10 +762,6 b" impl<'on_disk> super::dispatch::Dirstate"
         let node =
             self.get_or_insert(&filename).expect("no parse error in v1");
         node.data = NodeData::Entry(entry);
-        node.children = ChildNodes::default();
-        node.copy_source = None;
-        node.descendants_with_entry_count = 0;
-        node.tracked_descendants_count = 0;
     }
 
     fn add_file(