Merge branch 'bc/object-id'

Move from unsigned char[20] to struct object_id continues. * bc/object-id: match-trees: convert several leaf functions to use struct object_id tree-walk: convert tree_entry_extract() to use struct object_id struct name_entry: use struct object_id instead of unsigned char sha1[20] match-trees: convert shift_tree() and shift_tree_by() to use object_id test-match-trees: convert to use struct object_id sha1-name: introduce a get_oid() function