Merge branch 'jk/lose-name-path'

The "name_path" API was an attempt to reduce the need to construct
the full path out of a series of path components while walking a
tree hierarchy, but over time made less efficient because the path
needs to be flattened, e.g. to be compared with another path that
is already flat.  The API has been removed and its users have been
rewritten to simplify the overall code complexity.

* jk/lose-name-path:
  list-objects: pass full pathname to callbacks
  list-objects: drop name_path entirely
  list-objects: convert name_path to a strbuf
  show_object_with_name: simplify by using path_name()
  http-push: stop using name_path