vim-patch:9.1.0016: default diff highlighting is too noisy

Problem:  default diff highlighting is too noisy
Solution: Link diff highlighting groups to new
          Added/Removed/Changed, revert previous change
          (Romain Lafourcade)

Remove diff* links added in vim/vim#13776 and doc added in commit b1392be

The links added in vim/vim#13776 are way too noisy for the contexts in which
the `diff` syntax is applied (git commits, patches, etc.).

This commit:

- removes those links
- adds new default highlighting groups Added, Changed and
  Removed
- links the diff highlighting groups to those new defaults
- removes the doc changes
- adjusts the syntax_completion test for those newly added group
  names

Note: Changes to the default color schemes will be handled separately,
by adding links to those newly created Added/Removed/Changed
highlighting groups.

related: vim/vim#13776
closes vim/vim#13825

https://github.com/vim/vim/commit/124371c5a149a8c0c75c04b6c90ac11e71a0aa97

Co-authored-by: Romain Lafourcade <romain.lafourcade@razorfish.fr>

1 files changed, 3 insertions, 3 deletions

diff --git a/test/old/testdir/test_cmdline.vim b/test/old/testdir/test_cmdline.vim
index edc1d7439a..8210fc2310 100644
--- a/test/old/testdir/test_cmdline.vim
+++ b/test/old/testdir/test_cmdline.vim
@@ -431,11 +431,11 @@ func Test_highlight_completion()
 
   " A cleared group does not show up in completions.
   hi Anders ctermfg=green
-  call assert_equal(['Aardig', 'Anders'], getcompletion('A', 'highlight'))
+  call assert_equal(['Aardig', 'Added', 'Anders'], getcompletion('A', 'highlight'))
   hi clear Aardig
-  call assert_equal(['Anders'], getcompletion('A', 'highlight'))
+  call assert_equal(['Added', 'Anders'], getcompletion('A', 'highlight'))
   hi clear Anders
-  call assert_equal([], getcompletion('A', 'highlight'))
+  call assert_equal(['Added'], getcompletion('A', 'highlight'))
 endfunc
 
 func Test_getcompletion()