Extract a git repo from another one using git subtree

git-subtree-split-reminder.txt

# first create a branch in the parent repo
git subtree split -P path/to/folder/toExtract --branch branchName

# then create the directory for the external repo
mkdir myNewRepo
cd myNewRepo
git init
git remote add tempRemote path/to/parent/repo
# only getch what is needed no more to avoid cluttered git reflog in the new repo
git fetch --no-tags tempRemote branchName
git merge --ff tempRemote/branchName
# remove unused remote to avoid mistakes on parent repo
git remote remove tempRemote

# that's it the new repo is not cluttered

# if all is good you can remove the branch from parent Repo 
# and git rm the folder