Merge branch 'pw/status-with-corrupt-sequencer-state'

The code to read state files used by the sequencer machinery for
"git status" has been made more robust against a corrupt or stale
state files.

* pw/status-with-corrupt-sequencer-state:
status: do not report errors in sequencer/todo
sequencer: factor out todo command name parsing
sequencer: always allow tab after command name

diff --cc sequencer.c
Simple merge

diff --cc t/t7512-status-help.sh
Simple merge