vim-patch:9.1.0218: Unnecessary multiplications in backspace code (#28075)

Problem:  Unnecessary multiplications in backspace code, as
          "col / ts * ts" is the same as "col - col % ts".
Solution: Change "col / ts * ts" to "col - col % ts".  Adjust the loop
          and the comments ins_bs() to be easier to understand.  Update
          tests to reset 'smarttab' properly.
          (zeertzjq)

closes: vim/vim#14308

8ede7a0694

test/old/testdir/test_edit.vim

@@ -2065,7 +2065,10 @@ func Test_edit_revins()
   call setline(1, 'one two three')
   exe "normal! wi\nfour"
   call assert_equal(['one two three', 'ruof'], getline(1, '$'))
-  set revins&
+  set backspace=indent,eol,start
+  exe "normal! ggA\<BS>:"
+  call assert_equal(['one two three:ruof'], getline(1, '$'))
+  set revins& backspace&
   bw!
 endfunc
 
@@ -2156,7 +2159,7 @@ func s:check_backspace(expected)
   inoremap <buffer> <F2> <Cmd>let g:actual += [getline('.')]<CR>
   set backspace=indent,eol,start
 
-  exe "normal $i" .. repeat("\<BS>\<F2>", len(a:expected))
+  exe "normal i" .. repeat("\<BS>\<F2>", len(a:expected))
   call assert_equal(a:expected, g:actual)
 
   set backspace&
@@ -2166,9 +2169,12 @@ endfunc
 
 " Test that backspace works with 'smarttab' and mixed Tabs and spaces.
 func Test_edit_backspace_smarttab_mixed()
+  set smarttab
   call NewWindow(1, 30)
-  setlocal smarttab tabstop=4 shiftwidth=4
+  setlocal tabstop=4 shiftwidth=4
+
   call setline(1, "\t    \t         \t a")
+  normal! $
   call s:check_backspace([
         \ "\t    \t         \ta",
         \ "\t    \t        a",
@@ -2180,15 +2186,19 @@ func Test_edit_backspace_smarttab_mixed()
         \ ])
 
   call CloseWindow()
+  set smarttab&
 endfunc
 
 " Test that backspace works with 'smarttab' and 'varsofttabstop'.
 func Test_edit_backspace_smarttab_varsofttabstop()
   CheckFeature vartabs
 
+  set smarttab
   call NewWindow(1, 30)
-  setlocal smarttab tabstop=8 varsofttabstop=6,2,5,3
+  setlocal tabstop=8 varsofttabstop=6,2,5,3
+
   call setline(1, "a\t    \t a")
+  normal! $
   call s:check_backspace([
         \ "a\t    \ta",
         \ "a\t     a",
@@ -2199,13 +2209,17 @@ func Test_edit_backspace_smarttab_varsofttabstop()
         \ ])
 
   call CloseWindow()
+  set smarttab&
 endfunc
 
 " Test that backspace works with 'smarttab' when a Tab is shown as "^I".
 func Test_edit_backspace_smarttab_list()
+  set smarttab
   call NewWindow(1, 30)
-  setlocal smarttab tabstop=4 shiftwidth=4 list listchars=
+  setlocal tabstop=4 shiftwidth=4 list listchars=
+
   call setline(1, "\t    \t         \t a")
+  normal! $
   call s:check_backspace([
         \ "\t    \t        a",
         \ "\t    \t    a",
@@ -2215,15 +2229,19 @@ func Test_edit_backspace_smarttab_list()
         \ ])
 
   call CloseWindow()
+  set smarttab&
 endfunc
 
 " Test that backspace works with 'smarttab' and 'breakindent'.
 func Test_edit_backspace_smarttab_breakindent()
   CheckFeature linebreak
 
+  set smarttab
   call NewWindow(3, 17)
-  setlocal smarttab tabstop=4 shiftwidth=4 breakindent breakindentopt=min:5
+  setlocal tabstop=4 shiftwidth=4 breakindent breakindentopt=min:5
+
   call setline(1, "\t    \t         \t a")
+  normal! $
   call s:check_backspace([
         \ "\t    \t         \ta",
         \ "\t    \t        a",
@@ -2235,17 +2253,21 @@ func Test_edit_backspace_smarttab_breakindent()
         \ ])
 
   call CloseWindow()
+  set smarttab&
 endfunc
 
 " Test that backspace works with 'smarttab' and virtual text.
 func Test_edit_backspace_smarttab_virtual_text()
   CheckFeature textprop
 
+  set smarttab
   call NewWindow(1, 50)
-  setlocal smarttab tabstop=4 shiftwidth=4
+  setlocal tabstop=4 shiftwidth=4
+
   call setline(1, "\t    \t         \t a")
   call prop_type_add('theprop', {})
   call prop_add(1, 3, {'type': 'theprop', 'text': 'text'})
+  normal! $
   call s:check_backspace([
         \ "\t    \t         \ta",
         \ "\t    \t        a",
@@ -2258,6 +2280,7 @@ func Test_edit_backspace_smarttab_virtual_text()
 
   call CloseWindow()
   call prop_type_delete('theprop')
+  set smarttab&
 endfunc
 
 " vim: shiftwidth=2 sts=2 expandtab