the Git SCM

• https://git-scm.com
• https://git-scm.com/book – the online Pro Git book – quite a nice introduction (– and probably more than that)

what about GUIs?

• https://git-scm.com/downloads/guis
• https://git-scm.com/download/gui/linux – there are not just the “built-in GUI” tools
• https://git-scm.com/docs/git-gui – (“built-in”) GUI tool for committing
• https://git-scm.com/docs/gitk – (“built-in”) GUI tool for browsing

…

• https://git.wiki.kernel.org/index.php/Interfaces,_frontends,_and_tools
• https://git.wiki.kernel.org/index.php/Interfaces,_frontends,_and_tools#Emacs_integration