Merge branch 'ah/sequencer-rewrite-todo-fix'

When the user edits "rebase -i" todo file so that it starts with a "fixup", which would make it invalid, the command truncated the rest of the file before giving an error and returning the control back to the user. Stop truncating to make it easier to correct such a malformed todo file. * ah/sequencer-rewrite-todo-fix: sequencer: finish parsing the todo list despite an invalid first line