Knowledge Graph, being able to connect information from a variety of sources, has become very famous in recent years since its creation in 2012 by Google. Researchers in our community have leveraged Knowledge Graph to achieve various purposes such as improving API caveats accessibilities, generating answers to developer questions, and reasoning common software weaknesses, etc. In this work, we would like to leverage the knowledge graph concept for helping developers and project managers to comprehend software repositories. To this end, we design and implement a prototype tool called GitGraph, which takes as input a Git repository and constructs automatically a knowledge graph associated with the repository. Our preliminary experimental results show that GitGraph can correctly generate knowledge graphs for Git projects and the generated graphs are also useful for users to comprehend the projects. More specifically, the knowledge graph, on one hand, provides a graphic interface that users can interactively explore the integrated artefacts such as commits and changed methods, while on the other hand, provides a convenient means for users to search for advanced relations between the different artefacts.