patch 9.1.0899: default for 'backspace' can be set in C code

Problem:  default for 'backspace' can be set in C code
Solution: promote the default for 'backspace' from defaults.vim to the C
          code (Luca Saccarola)

closes: #16143

Signed-off-by: Luca Saccarola <github.e41mv@aleeas.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

runtime/defaults.vim

@@ -1,7 +1,7 @@
 " The default vimrc file.
 "
 " Maintainer:	The Vim Project <https://github.com/vim/vim>
-" Last Change:	2024 Nov 14
+" Last Change:	2024 Dec 01
 " Former Maintainer:	Bram Moolenaar <Bram@vim.org>
 "
 " This is loaded if no vimrc file was found.
@@ -33,9 +33,6 @@ silent! while 0
   set nocompatible
 silent! endwhile
 
-" Allow backspacing over everything in insert mode.
-set backspace=indent,eol,start
-
 set ruler		" show the cursor position all the time
 set showcmd		" display incomplete commands
 

runtime/doc/options.txt

@@ -1069,8 +1069,7 @@ A jump table for the options with a short description can be found at |Q_op|.
 	done with ":syntax on".
 
 							*'backspace'* *'bs'*
-'backspace' 'bs'	string	(default "", set to "indent,eol,start"
+'backspace' 'bs'	string	(Vim default: "indent,eol,start", Vi default: "")
-							    in |defaults.vim|)
 			global
 	Influences the working of <BS>, <Del>, CTRL-W and CTRL-U in Insert
 	mode.  This is a list of items, separated by commas.  Each item allows

runtime/doc/version9.txt

@@ -41611,6 +41611,8 @@ Changed~
 - 'rulerformat' now supports the |stl-%!| item
 - the default 'history' option value has been increased to 200 and removed
   from |defaults.vim|
+- the default 'backspace' option for Vim has been set to "indent,eol,start"
+  and removed from |defaults.vim|
 
 							*added-9.2*
 Added ~

src/optiondefs.h

@@ -414,9 +414,9 @@ static struct vimoption options[] =
 			    (char_u *)"light",
 #endif
 					    (char_u *)0L} SCTX_INIT},
-    {"backspace",   "bs",   P_STRING|P_VI_DEF|P_VIM|P_ONECOMMA|P_NODUP,
+    {"backspace",   "bs",   P_STRING|P_VIM|P_ONECOMMA|P_NODUP,
 			    (char_u *)&p_bs, PV_NONE, did_set_backspace, expand_set_backspace,
-			    {(char_u *)"", (char_u *)0L} SCTX_INIT},
+			    {(char_u *)"", (char_u *)"indent,eol,start"} SCTX_INIT},
     {"backup",	    "bk",   P_BOOL|P_VI_DEF|P_VIM,
 			    (char_u *)&p_bk, PV_NONE, NULL, NULL,
 			    {(char_u *)FALSE, (char_u *)0L} SCTX_INIT},

src/testdir/test_autocmd.vim

@@ -1279,8 +1279,8 @@ func Test_OptionSet()
   call assert_equal(g:opt[0], g:opt[1])
 
   " 14: Setting option backspace through :let"
-  let g:options = [['backspace', '', '', '', 'eol,indent,start', 'global', 'set']]
+  let g:options = [['backspace', 'indent,eol,start', 'indent,eol,start', 'indent,eol,start', '', 'global', 'set']]
-  let &bs = "eol,indent,start"
+  let &bs = ''
   call assert_equal([], g:options)
   call assert_equal(g:opt[0], g:opt[1])
 

src/testdir/test_digraph.vim

@@ -250,9 +250,12 @@ func Test_digraphs_option()
   call Put_Dig_BS("P","=")
   call assert_equal(['Р']+repeat(["₽"],2)+['П'], getline(line('.')-3,line('.')))
   " Not a digraph: this is different from <c-k>!
+  let _bs = &bs
+  set bs=
   call Put_Dig_BS("a","\<bs>")
   call Put_Dig_BS("\<bs>","a")
   call assert_equal(['','a'], getline(line('.')-1,line('.')))
+  let &bs = _bs
   " Grave
   call Put_Dig_BS("a","!")
   call Put_Dig_BS("!","e")

src/testdir/test_ins_complete.vim

@@ -1431,7 +1431,7 @@ func Test_complete_item_refresh_always()
   set completefunc=Tcomplete
   exe "normal! iup\<C-X>\<C-U>\<BS>\<BS>\<BS>\<BS>\<BS>"
   call assert_equal('up', getline(1))
-  call assert_equal(2, g:CallCount)
+  call assert_equal(6, g:CallCount)
   set completeopt&
   set completefunc&
   bw!

src/testdir/test_options.vim

@@ -486,7 +486,7 @@ func Test_set_completion_string_values()
   " but don't exhaustively validate their results.
   call assert_equal('single', getcompletion('set ambw=', 'cmdline')[0])
   call assert_match('light\|dark', getcompletion('set bg=', 'cmdline')[1])
-  call assert_equal('indent', getcompletion('set backspace=', 'cmdline')[0])
+  call assert_equal('indent,eol,start', getcompletion('set backspace=', 'cmdline')[0])
   call assert_equal('yes', getcompletion('set backupcopy=', 'cmdline')[1])
   call assert_equal('backspace', getcompletion('set belloff=', 'cmdline')[1])
   call assert_equal('min:', getcompletion('set briopt=', 'cmdline')[1])

src/version.c

@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    899,
 /**/
     898,
 /**/