update fork with original repo

gistfile1.txt

git remote add <remote_name> <original-repo>
# => add remote refs named (whatever) to targeted the original repo

git fetch <remote_name>
git merge <remote_name>/<branch-name>
# => safely gathers any commits from original repo and stores them in your local repo

** if auto-merging conflict, use `git diff --color` to check/edit the files 
   and commit it first before push to the remote repo