I发现了如何在新文件夹中的同一分支中复制文件夹并维护提交历史记录:
git clone <url>
git switch source-branch
a=$(git commit-tree -p heads/source-branch -m "Slice folder to prepare for copy with commit history" heads/source-branch:source-folder)
git update-ref refs/heads/temp-branch $a
git branch -vv
mkdir new-folder
touch new-folder/readme.md
git add .
commit -m "Commit new folder to prep for copy."
git merge --allow-unrelated-histories --no-commit -Xsubtree=new-folder temp-branch
git status
git add .
git commit -m "Commit a copy of source-folder with commit history."
git log --oneline
git push origin