Merge branch 'jc/sequencer-stopped-sha-simplify'

Recently the format of an internal state file "rebase -i" uses has been tightened up for consistency, which would hurt those who start "rebase -i" with old git and then continue with new git. Loosen the reader side a bit (which we may want to tighten again in a year or so). * jc/sequencer-stopped-sha-simplify: sequencer: tolerate abbreviated stopped-sha file