Emacs/emacs/Customizing-VC

From Get docs

28.1.13 Customizing VC

The variable vc-handled-backends determines which version control systems VC should handle. The default value is (RCS CVS SVN SCCS SRC Bzr Git Hg Mtn), so it contains all the version systems that are currently supported. If you want VC to ignore one or more of these systems, exclude its name from the list. To disable VC entirely, set this variable to nil.

The order of systems in the list is significant: when you visit a file registered in more than one system, VC uses the system that comes first in vc-handled-backends by default. The order is also significant when you register a file for the first time (see Registering).

General VC Options:    Options that apply to multiple back ends.
RCS and SCCS:    Options for RCS and SCCS.
CVS Options:    Options for CVS.