Merge branch 'jk/tree-name-and-depth-limit'

Merge branch 'jk/tree-name-and-depth-limit'

We now limit depth of the tree objects and maximum length of
pathnames recorded in tree objects.

* jk/tree-name-and-depth-limit:
  lower core.maxTreeDepth default to 2048
  tree-diff: respect max_allowed_tree_depth
  list-objects: respect max_allowed_tree_depth
  read_tree(): respect max_allowed_tree_depth
  traverse_trees(): respect max_allowed_tree_depth
  add core.maxTreeDepth config
  fsck: detect very large tree pathnames
  tree-walk: rename "error" variable
  tree-walk: drop MAX_TRAVERSE_TREES macro
  tree-walk: reduce stack size for recursive functions