patch 9.1.1507: symlinks are resolved on :cd commands

Problem:  File paths change from symlink to target path after :cd command
          when editing files through symbolic links
Solution: Add "~" flag to 'cpoptions' to control symlink resolution.
          When not included (default), symlinks are resolved maintaining
          backward compatibility. When included, symlinks are preserved
          providing the improved behavior. (glepnir)

related: neovim/neovim#15695
closes: #17628

Signed-off-by: glepnir <glephunter@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/testdir/test_options.vim b/src/testdir/test_options.vim
index cb5636e..21e4a03 100644
--- a/src/testdir/test_options.vim
+++ b/src/testdir/test_options.vim
@@ -2273,7 +2273,7 @@
     qall
   [CODE]
   if RunVim([], after, '')
-    call assert_equal(['aAbBcCdDeEfFgHiIjJkKlLmMnoOpPqrRsStuvwWxXyZz$!%*-+<>#{|&/\.;',
+    call assert_equal(['aAbBcCdDeEfFgHiIjJkKlLmMnoOpPqrRsStuvwWxXyZz$!%*-+<>#{|&/\.;~',
           \            'AS'], readfile('X_VIM_POSIX'))
   endif
 
@@ -2528,7 +2528,7 @@
         \ ['completeopt', 'popup', 'a123'],
         \ ['completepopup', 'width:20', 'border'],
         \ ['concealcursor', 'v', 'xyz'],
-        \ ['cpoptions', 'HJ', '~'],
+        \ ['cpoptions', 'HJ', 'Q'],
         \ ['cryptmethod', 'zip', 'a123'],
         \ ['cursorlineopt', 'screenline', 'a123'],
         \ ['debug', 'throw', 'a123'],