Merge branch 'rs/commit-list-sort-in-batch'

Setting up a revision traversal with many starting points was inefficient as these were placed in a date-order priority queue one-by-one. By René Scharfe (3) and Junio C Hamano (1) * rs/commit-list-sort-in-batch: mergesort: rename it to llist_mergesort() revision: insert unsorted, then sort in prepare_revision_walk() commit: use mergesort() in commit_list_sort_by_date() add mergesort() for linked lists