require-final-newline

require-final-newline is a variable defined in `files.el'.
Its value is

nil

• This variable is safe as a file local variable if its value
  satisfies the predicate `symbolp'.

Documentation:
Whether to add a newline automatically at the end of the file.

A value of t means do this only when the file is about to be saved.
A value of `visit' means do this right after the file is visited.
A value of `visit-save' means do it at both of those times.
Any other non-nil value means ask user whether to add a newline, when saving.
A value of nil means don't add newlines.

Certain major modes set this locally to the value obtained
from `mode-require-final-newline'.

You can customize this variable.