simplemerge: rewrite `merge_lines()` using `merge_groups()`
Simple is better.
Differential Revision: https://phab.mercurial-scm.org/D11967
%include map-cmdline.default
[templates]
changeset = '{cset}{branches}{bookmarks}{tags}{lphase}{parents}{luser}{ldate}{summary}\n'
changeset_verbose = '{cset}{branches}{bookmarks}{tags}{lphase}{parents}{luser}{ldate}{lfiles}{lfile_copies_switch}{description}\n'