Variable: delete-old-versions
delete-old-versions is a customizable variable defined in files.el.gz.
Value
nil
Documentation
If t, delete excess numbered backup files silently.
If nil, ask confirmation. Any other value prevents any trimming.
See version-control, kept-old-versions, kept-new-versions
and dired-kept-versions for more about keeping and deleting old
versioned (a.k.a. "numbered") backup files.
Probably introduced at or before Emacs version 19.26.
Source Code
;; Defined in /usr/src/emacs/lisp/files.el.gz
(defcustom delete-old-versions nil
"If t, delete excess numbered backup files silently.
If nil, ask confirmation. Any other value prevents any trimming.
See `version-control', `kept-old-versions', `kept-new-versions'
and `dired-kept-versions' for more about keeping and deleting old
versioned (a.k.a. \"numbered\") backup files."
:type '(choice (const :tag "Delete" t)
(const :tag "Ask" nil)
(other :tag "Leave" other))
:group 'backup)