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

diff --cc .gitignore
index 5a0782fe815a299a3a79ea15269aa6e0a7738a56,1787c8185d5a750afc4020278cd569eedd173875..83a5c9df1b2c21e21be9375ac01be94c8dcf941a
--- 1/.gitignore
--- 2/.gitignore
+++ b/.gitignore
@@@ -181,7 -180,9 +181,8 @@@
  /test-index-version
  /test-line-buffer
  /test-match-trees
+ /test-mergesort
  /test-mktemp
 -/test-obj-pool
  /test-parse-options
  /test-path-utils
  /test-run-command

diff --cc Makefile
index 172e924a29521886dc4d365302ee12ed73c357d5,330a7d5ae99eee96472261b4eddd063dd533edaa..f1caae8a827e7381df8226b36485409dfca71642
--- 1/Makefile
--- 2/Makefile
+++ b/Makefile
@@@ -481,7 -465,9 +481,8 @@@ TEST_PROGRAMS_NEED_X += test-genrando
  TEST_PROGRAMS_NEED_X += test-index-version
  TEST_PROGRAMS_NEED_X += test-line-buffer
  TEST_PROGRAMS_NEED_X += test-match-trees
+ TEST_PROGRAMS_NEED_X += test-mergesort
  TEST_PROGRAMS_NEED_X += test-mktemp
 -TEST_PROGRAMS_NEED_X += test-obj-pool
  TEST_PROGRAMS_NEED_X += test-parse-options
  TEST_PROGRAMS_NEED_X += test-path-utils
  TEST_PROGRAMS_NEED_X += test-run-command

diff --cc commit.c
Simple merge

diff --cc revision.c
Simple merge