Merge branch 'ab/leakfix'

Merge branch 'ab/leakfix'

Plug various memory leaks.

* ab/leakfix:
  pull: fix a "struct oid_array" memory leak
  cat-file: fix a common "struct object_context" memory leak
  gc: fix a memory leak
  checkout: avoid "struct unpack_trees_options" leak
  merge-file: fix memory leaks on error path
  merge-file: refactor for subsequent memory leak fix
  cat-file: fix a memory leak in --batch-command mode
  revert: free "struct replay_opts" members
  submodule.c: free() memory from xgetcwd()
  clone: fix memory leak in wanted_peer_refs()
  check-ref-format: fix trivial memory leak