Merge branch 'pw/status-rebase-todo' into seen

The display of the rebase todo list in "git status" has been
improved to correctly abbreviate object IDs for more commands and
avoid misinterpreting refs as object IDs.

* pw/status-rebase-todo:
  status: improve rebase todo list parsing
  sequencer: factor out parsing of todo commands

diff --cc sequencer.c
Simple merge

diff --cc sequencer.h
Simple merge

diff --cc wt-status.c
Simple merge