find-backup-file-name

find-backup-file-name is a compiled Lisp function in `files.el'.

(find-backup-file-name FN)

Find a file name for a backup file FN, and suggestions for deletions.
Value is a list whose car is the name for the backup file
and whose cdr is a list of old versions to consider deleting now.
If the value is nil, don't make a backup.
Uses `backup-directory-alist' in the same way as
`make-backup-file-name--default-function' does.