I don't know which app did you see, but https://github.com/ is a large project dedicated to code hosting. You can use it to collaborate with somebody to create, but you also can use it as a code hosting to access your code from everywhere (There even is online code editor). I didn't mention automated backups, and other useful things.
GitHub is a great place to learn programming. https://github.com/teeworlds/teeworlds is my home page, since I'm interested in game developing, and I found out there are a lot of things I have to learn:
Scripting in Lua and Python
How to configure project files
Poor me, With C++, OpenGL and SDL I'm just at the beginning of the road :(