Pre-release documentation. PostgreSQL 19beta4 is a testing release. The final release may differ.
Appendix I. The Source Code Repository
Table of Contents
The PostgreSQL source code is stored and managed using the Git version control system. A public mirror of the master repository is available; it is updated within a minute of any change to the master repository.
Our wiki, https://wiki.postgresql.org/wiki/Working_with_Git, has some discussion on working with Git.
Report a documentation issue
Read the upstream documentation. For corrections, first check the current manual.