vim-patch:9.1.2037: undo: cursor position not correctly restored (#37195)

Problem:  undo: cursor position not correctly restored
Solution: Do not override the saved cursor position (altermo)

closes: vim/vim#19052

https://github.com/vim/vim/commit/a722da29c128576d581f451f3f6282de27680d9f

Co-authored-by: altermo <107814000+altermo@users.noreply.github.com>

src/nvim/undo.c

@@ -2298,15 +2298,17 @@ static void u_undoredo(bool undo, bool do_buf_event)
 
     // Decide about the cursor position, depending on what text changed.
     // Don't set it yet, it may be invalid if lines are going to be added.
-    if (top < newlnum) {
+    {
       // If the saved cursor is somewhere in this undo block, move it to
       // the remembered position.  Makes "gwap" put the cursor back
       // where it was.
       linenr_T lnum = curhead->uh_cursor.lnum;
       if (lnum >= top && lnum <= top + newsize + 1) {
         new_curpos = curhead->uh_cursor;
-        newlnum = new_curpos.lnum - 1;
-      } else {
+        // We don't want other entries to override saved cursor
+        // position.
+        newlnum = -1;
+      } else if (top < newlnum) {
         // Use the first line that actually changed.  Avoids that
         // undoing auto-formatting puts the cursor in the previous
         // line.

test/functional/ui/bufhl_spec.lua

@@ -282,9 +282,9 @@ describe('Buffer highlighting', function()
       screen:expect {
         grid = [[
         a {5:longer} example                        |
-        ^in {6:order} to {7:de}{5:monstr}{7:ate}                 |
+        in {6:order} to {7:de}{5:monstr}{7:ate}                 |
         {7:combin}{8:ing}{9: hi}ghlights                    |
-        {9:from }{8:diff}{7:erent} sources                  |
+        {9:from }{8:diff}{7:erent} source^s                  |
         {1:~                                       }|*3
         1 change; before #2  {MATCH:.*}|
       ]],

test/old/testdir/test_undo.vim

@@ -911,5 +911,16 @@ func Test_load_existing_undofile()
   bw!
 endfunc
 
+func Test_restore_cursor_position_after_undo()
+  CheckFeature persistent_undo
+  sp samples/test_undo.txt
+
+  3 | exe "norm! gqk" | undojoin | 1 delete
+  call assert_equal(1, line('.'))
+  norm! u
+  call assert_equal(3, line('.'))
+  bw!
+endfunc
+
 
 " vim: shiftwidth=2 sts=2 expandtab