add-name-to-fileadd-name-to-file is an interactive built-in function in `
C source code'. (add-name-to-file FILE NEWNAME &optional OK-IF-ALREADY-EXISTS) Give FILE additional name NEWNAME. Both args must be strings. Signals a `file-already-exists' error if a file NEWNAME already exists unless optional third argument OK-IF-ALREADY-EXISTS is non-nil. A number as third arg means request confirmation if NEWNAME already exists. This is what happens in interactive use with M-x.