Merge branch 'sb/fmt-merge-msg'

* sb/fmt-merge-msg: fmt-merge-msg: hide summary option fmt-merge-msg: remove custom string_list implementation string-list: add unsorted_string_list_lookup() fmt-merge-msg: use pretty.c routines t6200: test fmt-merge-msg more t6200: modernize with test_tick fmt-merge-msg: be quiet if nothing to merge