file2repo.md

Push an individual file from a repo to a new repo and keep command history associated with that file:

git clone <original repo url> temp-repo
cd temp-repo
git remote rm origin
git rm -rf .
git checkout HEAD -- <filename>
git commit -m "<commit message>"
git remote add origin <new repo url> # comments
git pull 
git push -f

Optional: Add new repo as submodule of original repo

git submodule add <new repo url>

Keep the method but rewrite the history.

git checkout --orphan <new_branch> <your_last_SHA>
git branch -d master # delete the original master
git branch -m master # rename current branch to master
git push -f origin master

If you want/need to keep longer history, you can --orphan an earlier SHA and cherry-pick subsequent commits from the origin master (before you delete it, of course).