Do not set indent-line-function in text-mode

For discussion, see thread starting at:
https://lists.gnu.org/archive/html/emacs-devel/2019-03/msg01012.html
* lisp/textmodes/text-mode.el (text-mode): Do not reset
indent-line-function to its global default value of indent-relative.
* doc/lispref/modes.texi (Example Major Modes):
* etc/NEWS: Document change accordingly.

doc/lispref/modes.texi

@@ -1292,15 +1292,10 @@ Turning on Text mode runs the normal hook `text-mode-hook'."
 @end group
 @group
   (setq-local text-mode-variant t)
-  (setq-local require-final-newline mode-require-final-newline)
-  (setq-local indent-line-function #'indent-relative))
+  (setq-local require-final-newline mode-require-final-newline))
 @end group
 @end smallexample
 
-@noindent
-(The last line is redundant nowadays, since @code{indent-relative} is
-the default value, and we'll delete it in a future version.)
-
 @cindex @file{lisp-mode.el}
   The three Lisp modes (Lisp mode, Emacs Lisp mode, and Lisp Interaction
 mode) have more features than Text mode and the code is correspondingly

etc/NEWS

@@ -1371,6 +1371,15 @@ ending character were silently omitted.
 For example, '(rx (any "@z-a" (?9 . ?0)))' would match '@' only.
 Now, such rx expressions generate an error.
 
++++
+** 'text-mode' no longer sets the value of 'indent-line-function'.
+The global value of 'indent-line-function', which defaults to
+'indent-relative', will no longer be reset locally when turning on
+'text-mode'.
+
+To get back the old behavior, add a function to 'text-mode-hook' which
+performs (setq-local indent-line-function #'indent-relative).
+
 
 * Lisp Changes in Emacs 27.1
 

lisp/textmodes/text-mode.el

@@ -105,8 +105,7 @@ You can thus get the full benefit of adaptive filling
 \\{text-mode-map}
 Turning on Text mode runs the normal hook `text-mode-hook'."
   (setq-local text-mode-variant t)
-  (setq-local require-final-newline mode-require-final-newline)
-  (setq-local indent-line-function #'indent-relative))
+  (setq-local require-final-newline mode-require-final-newline))
 
 (define-derived-mode paragraph-indent-text-mode text-mode "Parindent"
   "Major mode for editing text, with leading spaces starting a paragraph.