Adding a particular subfolder (from another git repo) to another subfolder (of other git repo) preserving the history

subfolder_to_git.md

This is definitely not the best method but this is something that worked for me

• clone the Repo (from where you want the subdirectory)

git clone --no-hardlinks repo2

• Select the folder you want to keep

cd repo2
git filter-branch --subdirectory-filter path/to/subfolder HEAD -- --all

• Remove everything else

git reset --hard
git gc --aggressive
git prune
git remote rm origin

• Add the Repo where you want this subdirectory in and clone it

git remote add origin repo1
git pull origin master --allow-unrelated-histories

• Commit and Push

git add --all -A
git commit -m "whatever"
git push origin master