Variable: display-line-numbers-widen
display-line-numbers-widen is a customizable and buffer-local variable
defined in xdisp.c.
Documentation
Non-nil means display line numbers disregarding any narrowing.
This variable was added, or its default value changed, in Emacs 26.1.
Source Code
// Defined in /usr/src/emacs/src/xdisp.c
DEFVAR_BOOL ("display-line-numbers-widen", display_line_numbers_widen,
doc: /* Non-nil means display line numbers disregarding any narrowing. */);