Edit commit message in the past
patch method
#create a patch file for each commit between HEAD and %commit_to_edit%
git format-patch %commit_to_edit%
#move HEAD to %commit_to_edit%
git reset --hard %commit_to_edit%
#apply all patches
ls *.patch | sort -n | xargs -I[] sh -c "git am < []"
#delete all patches files
rm *.patch
rebase -i method
git rebase -i %commit_to_edit%^
#in the editor, replace "pick" by "reword" for the commit to edit
#save and quit
#in second editor, edit message
#save and quit