Due to GitHub's nature, a repository contains many metadata such as commits over time, who contributed what, number of contributors, number of forks, and even site referrals to various files.
GitHub provides some useful graphs and data from which you can deduct the information you require.
Graphs can be accessed through the right sidebar of a repository:
To better understand how this works, pick up a project with high traffic; for example, https://github.com/twbs/bootstrap/graphs. The default tab is the Contributors tab and also the one we will explore next.
An overview of the top 100 contributors ...