Merge branch 'cc/replace-graft'

"git replace" learned a "--graft" option to rewrite parents of a commit. * cc/replace-graft: replace: add test for --graft with a mergetag replace: check mergetags when using --graft replace: add test for --graft with signed commit replace: remove signature when using --graft contrib: add convert-grafts-to-replace-refs.sh Documentation: replace: add --graft option replace: add test for --graft replace: add --graft option replace: cleanup redirection style in tests