vim $(git --exec-path)/git-rebase--interactive
GIT_SEQUENCE_EDITOR="sed -i '' -e 's/^pick/reword/g'" git rebase -i --root
GIT_SEQUENCE_EDITOR=: git rebase -i YOUR_SHA -x "git commit --amend --reset-author -CHEAD"
http://stackoverflow.com/a/25815116/1104534
git filter-branch --env-filter 'GIT_COMMITTER_DATE=$GIT_AUTHOR_DATE; export GIT_COMMITTER_DATE'
http://stackoverflow.com/a/11179245/1104534
git filter-branch --msg-filter 'sed -e "s/^fixup! //"'