Git : How to add an existing local folder into a git repository?

This is quite simple, in fact, this is one of the suggestions that bitbucket gives when new repo is created
 

if we have an existing repository, then that can be initialized to git by the below command

cd /
git init

git remote add origin https://myusername@bitbucket.org/myusername/mytestapp-ios.git
git push -u origin master

now when committing if getting the below error,

git push

No refs in common and none specified; doing nothing.

Perhaps you should specify a branch such as 'master'.

Everything up-to-date

Below to be done to set the upstream folder. 

git push --set-upstream origin master