vim-patch:9.1.1885: Wrong restored cursor pos when re-entering buffer after changes

Problem:  Wrong restored cursor position when re-entering a buffer
          previously viewed in a window after making changes to the same
          buffer in another window.
Solution: Adjust per-window "last cursor" positions on buffer changes.
          (zeertzjq)

closes: vim/vim#18655

b2e6b328da

test/old/testdir/test_buffer.vim

@@ -619,17 +619,48 @@ func Test_switch_to_previously_viewed_buffer()
   vsplit
 
   call cursor(100, 3)
+  call assert_equal('100', getline('.'))
   edit Xotherbuf
   buffer Xviewbuf
   call assert_equal([0, 100, 3, 0], getpos('.'))
+  call assert_equal('100', getline('.'))
 
+  edit Xotherbuf
+  wincmd p
+  normal! gg10dd
+  wincmd p
+  buffer Xviewbuf
+  call assert_equal([0, 90, 3, 0], getpos('.'))
+  call assert_equal('100', getline('.'))
+
+  edit Xotherbuf
+  wincmd p
+  normal! ggP
+  wincmd p
+  buffer Xviewbuf
+  call assert_equal([0, 100, 3, 0], getpos('.'))
+  call assert_equal('100', getline('.'))
+
+  edit Xotherbuf
+  wincmd p
+  normal! 96gg10ddgg
+  wincmd p
+  buffer Xviewbuf
+  " The original cursor line was deleted, so cursor is restored to the start
+  " of the line before the deleted range.
+  call assert_equal([0, 95, 1, 0], getpos('.'))
+  call assert_equal('95', getline('.'))
+
+  normal! u
   exe win_id2win(oldwin) .. 'close'
   setlocal bufhidden=hide
 
   call cursor(200, 3)
+  call assert_equal('200', getline('.'))
   edit Xotherbuf
   buffer Xviewbuf
   call assert_equal([0, 200, 3, 0], getpos('.'))
+  call assert_equal('200', getline('.'))
 
   bwipe! Xotherbuf
   bwipe! Xviewbuf