Adds du/dU keymaps to fugitive's :Git status buffer for opening unified
diffs instead of side-by-side diffs:
- du opens horizontal split (mirrors dd)
- dU opens vertical split (mirrors dv)
Parses status buffer lines to extract filename and detect section
(staged/unstaged/untracked). For staged files, diffs index vs HEAD.
For unstaged files, diffs working tree vs index.
Configurable via vim.g.diffs.fugitive.horizontal/vertical (set to
false to disable).
Compares current buffer against any git revision (default HEAD), opens result
with full diffs.nvim syntax highlighting. Follows fugitive convention:
:Gdiff/:Gvdiff open vertical split, :Ghdiff opens horizontal split.
