GCC multi-version development layout

[Heime]

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When building GCC from a cloned Git source tree using separate 
directories (as recommended), the directory structure follows 
a clean separation of source, build artifacts, and final 
installation. 

With different version of gcc, how would be the typical layout 
for specific branches to make patch changes to different gcc 
versions with multiple builds and install?

What are good books to read about version control useful for
work on gcc branches.