fix(git): show untracked files when comparing working tree (sindrets#587)

Show untracked files when the right side of the comparison is the
working tree (LOCAL), not just when comparing index vs working tree.
This allows seeing untracked files in more diff scenarios.

Fixes sindrets#584

Author: KEY60228

lua/diffview/vcs/adapters/git/init.lua

@@ -1674,9 +1674,8 @@ function GitAdapter:show_untracked(opt)
   opt = opt or {}
 
   if opt.revs then
-    -- Never show untracked files when comparing against anything other than
-    -- the index
-    if not (opt.revs.left.type == RevType.STAGE and opt.revs.right.type == RevType.LOCAL) then
+    -- Show untracked files when comparing against the working tree (LOCAL)
+    if opt.revs.right.type ~= RevType.LOCAL then
       return false
     end
   end