Problem: running :e on a :Gdiff buffer cleared all content because
diffs:// buffers had no BufReadCmd handler. Neovim tried to read the
buffer name as a file path, found nothing on disk, and emptied the
buffer. This affected all three buffer creation paths (gdiff,
gdiff_file, gdiff_section).
Solution: register a BufReadCmd autocmd for diffs://* that parses the
URL and regenerates diff content from git. Change buffer options from
nofile/wipe to nowrite/delete (matching fugitive's approach) so
buffer-local autocmds and variables survive across unload/reload
cycles. Store old filepath as buffer variable for rename support.
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.
