Merge branch 'cm/rebase-i'

"rebase -i" is getting cleaned up and also enhanced. * cm/rebase-i: doc/git-rebase: add documentation for fixup [-C|-c] options rebase -i: teach --autosquash to work with amend! t3437: test script for fixup [-C|-c] options in interactive rebase rebase -i: add fixup [-C | -c] command sequencer: use const variable for commit message comments sequencer: pass todo_item to do_pick_commit() rebase -i: comment out squash!/fixup! subjects from squash message sequencer: factor out code to append squash message rebase -i: only write fixup-message when it's needed