https://doc.sagemath.org/html/en/developer/git_setup.html#installing-git

On mac, it should refer to Xcode.
The linux install instructions should be autogenerated.

Depends on #29655

CC: @jhpalmieri @orlitzky @fchapoton @dimpase @Etn40ff

Component: documentation

Keywords: sd111

Issue created by migration from https://trac.sagemath.org/ticket/30201