Merge branch 'js/prepare-sequencer'

Update of the sequencer codebase to make it reusable to reimplement "rebase -i" continues. * js/prepare-sequencer: (27 commits) sequencer: mark all error messages for translation sequencer: start error messages consistently with lower case sequencer: quote filenames in error messages sequencer: mark action_name() for translation sequencer: remove overzealous assumption in rebase -i mode sequencer: teach write_message() to append an optional LF sequencer: refactor write_message() to take a pointer/length sequencer: roll back lock file if write_message() failed sequencer: stop releasing the strbuf in write_message() sequencer: left-trim lines read from the script sequencer: support cleaning up commit messages sequencer: support amending commits sequencer: allow editing the commit message on a case-by-case basis sequencer: introduce a helper to read files written by scripts sequencer: prepare for rebase -i's commit functionality sequencer: remember the onelines when parsing the todo file sequencer: get rid of the subcommand field sequencer: avoid completely different messages for different actions sequencer: strip CR from the todo script sequencer: completely revamp the "todo" script parsing ...