fix: show untracked files when comparing working tree

[KEY60228]

Summary

This PR fixes an issue where untracked files are not displayed when comparing the working tree against a specific commit using DiffviewOpen.

Fixes #584

Problem

The current implementation only shows untracked files when comparing the index (stage) against the working tree (DiffviewOpen with no arguments). However, the documentation states:

" Diff the working tree against a specific commit:
:DiffviewOpen HEAD~2

When comparing the working tree against a commit, users would expect to see all changes including untracked files, but they are currently hidden.

Solution

Modified the condition in GitAdapter:show_untracked() to check if the right side of the comparison is the working tree (LOCAL), rather than requiring both specific left (STAGE) and right (LOCAL) types.

Before

-- Only show untracked files for STAGE..LOCAL comparison
if not (opt.revs.left.type == RevType.STAGE and opt.revs.right.type == RevType.LOCAL) then
  return false
end

After

-- Show untracked files when comparing against the working tree (LOCAL)
if opt.revs.right.type ~= RevType.LOCAL then
  return false
end

Testing

• DiffviewOpen - Shows untracked files (existing behavior preserved)
• DiffviewOpen HEAD~1 - Now shows untracked files
• DiffviewOpen main - Now shows untracked files
• DiffviewOpen HEAD~1 -uno - Hides untracked files as expected
• DiffviewOpen HEAD~1..HEAD - Does not show untracked files (correct, as neither side is LOCAL)

Notes

• The -u/--untracked-files flag now works correctly for all working tree comparisons
• Users can still use -uno to hide untracked files if desired
• This change aligns the behavior with the documentation and user expectations