Merge branch 'nd/tree-walk-with-repo'

Merge branch 'nd/tree-walk-with-repo'

The tree-walk API learned to pass an in-core repository
instance throughout more codepaths.

* nd/tree-walk-with-repo:
  t7814: do not generate same commits in different repos
  Use the right 'struct repository' instead of the_repository
  match-trees.c: remove the_repo from shift_tree*()
  tree-walk.c: remove the_repo from get_tree_entry_follow_symlinks()
  tree-walk.c: remove the_repo from get_tree_entry()
  tree-walk.c: remove the_repo from fill_tree_descriptor()
  sha1-file.c: remove the_repo from read_object_with_reference()