how to add the git to existing project code example

Example 1: git push existing repo

cd existing_folder
git init
git remote add origin https://gitlab.com/abc.git
git add .
git commit -m "Initial commit"
git push -u origin master

Example 2: turn a folder into a git repo

$ git filter-branch --prune-empty --subdirectory-filter FOLDER-NAME  BRANCH-NAME 
  # Filter the specified branch in your directory and remove empty commits
  > Rewrite 48dc599c80e20527ed902928085e7861e6b3cbe6 (89/89)
  > Ref 'refs/heads/BRANCH-NAME' was rewritten