Merge branch 'pw/rebase-i-error-message'

When the user adds to "git rebase -i" instruction to "pick" a merge commit, the error experience is not pleasant. Such an error is now caught earlier in the process that parses the todo list. * pw/rebase-i-error-message: rebase -i: improve error message when picking merge rebase -i: pass struct replay_opts to parse_insn_line()