Source code repository
The TYPO3 source code is managed using a distributed revision control and source code management (SCM) system called Git. Information about Git and the review system Gerrit can be found in the TYPO3 wiki.
The source code repository can also be browsed conveniently using our project management app Redmine at TYPO3 Forge.
Gerrit review workflow
Gerrit is the system used by the TYPO3 core team to review and finally add new contributions to the core. TYPO3's Gerrit interface is located at review.typo3.org. Gerrit handles the whole review process and is a gatekeeper in front of the official TYPO3 Git repository on git.typo3.org. Every change has to pass a review process in Gerrit, which later pushes the change to the repository.
The Gerrit Review Worklow is decribed in the Contribution Workflow Guide.
Information about the way bugs are handled for TYPO3 CMS can be found in the bug fixing pages. You may also refer to the TYPO3 CMS issue tracker.