git-split-fixups.sh

#!/usr/bin/env bash
set -euo pipefail
IFS=$'\n\t'

git reset .

if [[ -e ".git/rebase-merge/interactive" ]]; then
	git reset HEAD~1
fi

git diff --name-only \
| while read FILE; do
	echo "$FILE"
	CHANGED_IN="$(git log --pretty='%H' origin/master...HEAD -- "$FILE")"
	if [[ -z "$CHANGED_IN" ]]; then
		echo "$FILE is first changed in this commit, no commit to fixup found"
	fi
	for COMMIT in $CHANGED_IN; do
		set -x
		git add "$FILE"
		git commit --fixup "$COMMIT"
		set +x
		break
	done
done

In Git interactive rebase

# ...
pick 9923cc6 prepare LeoExpress\Connection type
exec git split-fixups
pick 7842763 ScheduleEntryList::fromPrices
# ...