High level Architecture and Flow of Source Code

As part of this issue,

To have a high level design of the Source Code project which will visualise the components/features we have, how they are interacting/dependent on each other, Dependencies between Source Code and other teams.

This would help to give a clear picture to anyone like PM, EM, Team, New Hires, Other teams.

Better to keep the information at a high level for better understanding and easy maintenance.

Ideas

1. Repository -> raw repository
2. Gitaly - Rails interaction
3. Redis cache for repositories
4. PostReceive -> how the commit pushed
5. Pull mirrors process
6. Forks
7. Pool repositories