Merge branch 'ah/plugleaks'

Merge branch 'ah/plugleaks'

Leak plugging.

* ah/plugleaks:
  reset: clear_unpack_trees_porcelain to plug leak
  builtin/rebase: fix options.strategy memory lifecycle
  builtin/merge: free found_ref when done
  builtin/mv: free or UNLEAK multiple pointers at end of cmd_mv
  convert: release strbuf to avoid leak
  read-cache: call diff_setup_done to avoid leak
  ref-filter: also free head for ATOM_HEAD to avoid leak
  diffcore-rename: move old_dir/new_dir definition to plug leak
  builtin/for-each-repo: remove unnecessary argv copy to plug leak
  builtin/submodule--helper: release unused strbuf to avoid leak
  environment: move strbuf into block to plug leak
  fmt-merge-msg: free newly allocated temporary strings when done