vc-handled-backends

vc-handled-backends is a variable defined in `vc-hooks.el'.
Its value is

(RCS CVS SVN SCCS SRC Bzr Git Hg Mtn)

Documentation:
List of version control backends for which VC will be used.
Entries in this list will be tried in order to determine whether a
file is under that sort of version control.
Removing an entry from the list prevents VC from being activated
when visiting a file managed by that backend.
An empty list disables VC altogether.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 25.1 of Emacs.