patch 8.2.4996: setbufline() may change Visual selection

Problem:    setbufline() may change Visual selection. (Qiming Zhao)
Solution:   Disable Visual mode when using another buffer. (closes #10466)

src/testdir/test_bufline.vim

@@ -222,4 +222,20 @@ func Test_appendbufline_redraw()
   call delete('XscriptMatchCommon')
 endfunc
 
+func Test_setbufline_select_mode()
+  new
+  call setline(1, ['foo', 'bar'])
+  call feedkeys("j^v2l\<C-G>", 'nx')
+
+  let bufnr = bufadd('Xdummy')
+  call bufload(bufnr)
+  call setbufline(bufnr, 1, ['abc'])
+
+  call feedkeys("x", 'nx')
+  call assert_equal(['foo', 'x'], getline(1, 2))
+
+  exe "bwipe! " .. bufnr
+  bwipe!
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab