Help modify diff behavior when using neovim as git difftool

[vlad-tim]

When I make a diff of two files using nvimdiff as a git difftool it does not look they way I want. More specifically, removed lines are visualized as added instead of being indicated as removed. When I run git difftool main.md this is what I see:

If I execute the same command using VSCode as difftool (i.e. `code --wait --diff $LOCAL $REMOTE), the result matches my expectations and looks like this:

Is there a way to achieve the desired look? I would like make removed lines have red background and added lines have green background.

[clason]

Just fix your colorscheme. (Use :Inspect to find out the used highlight groups you need to customize.)

[vlad-tim]

I tried to run :Inspect file keeping the cursor on the line with a problem, but it displays the error:

No items found at position 3,0 in buffer 1

I even tried to upgrade nvim to the nightly version, but result is the same.

[clason]

:h hl-DiffDelete

[vlad-tim]

I added highlight DiffDelete guifg=None guibg=#ff0000 to the configuration, and result is the following:

The background color on the right side became brighter. With that said, it may be not a problem with the color scheme, but something else. May my help request be re-opened?

[clason]

What else could it be a problem with? It's unclear what exactly you're asking for here. The result you stated in your question can be achieved by highlighting DiffDelete and DiffAdd.

[vlad-tim]

Assuming @zeertzjq is right and both removed and added lines are DiffAdd , then it is not clear to me how to distinguish them and paint differently.

[clason]

Of course not, that would make zero sense. The added line is DiffAdd, and the removed line is DiffDelete.

[zeertzjq]

|hl-DiffAdd|	DiffAdd		Added (inserted) lines.  These lines exist in
				this buffer but not in another.
|hl-DiffDelete|	DiffDelete	Deleted lines.  Also called filler lines,
				because they don't really exist in this
				buffer.

These are not removed lines. They are added lines, so you should see :h hl-DiffAdd and :h 'winhighlight'. Try this:

autocmd BufWinEnter * if &diff && argidx() == 0 | setlocal winhighlight=DiffAdd:DiffDelete,DiffDelete:DiffAdd | endif

[clason]

Sigh. This is now a different example than in your original question.

[vlad-tim]

I hope it helped to clarify the question and avoid confusion. It is still unclear to me if there is a solution.

[clason]

I suspect not. You can customize the colors, but not which lines are shown.

[zeertzjq]

Try this:

autocmd BufWinEnter * if &diff && argidx() == 0 | setlocal winhighlight=DiffAdd:DiffDelete,DiffDelete:DiffAdd | endif

[vlad-tim]

Oh, wow, it did the trick!

(I have been trying to wrap my head around winhighlight after reading you earlier message, but couldn't figure it out)

[bew]

I think the question is how diff highlights are computed: comparaison vs before/after

The diff in (n)vim shows you the difference compared to the other file. So the left file has 1 added line (in green) "compared to the right file", and the right file has 1 removed line "compared to the left file". But (n)vim doesn't have a concept of the 'current' file.

In git / vscode /.. it has this distinction of the 'current' file (right) and what it was before (left).
When showing the old file only deleted lines are highlighted, and on the 'current' file only new lines are highlighted.

[clason]

So you're not asking about the colors, but about the hatchings. For the deleted lines, see :h 'fillchars'. For the added lines, this is not possible.

[bew]

It's not about the hatching either, but about where deleted/added lines are shown.

There is no way currently afaik to only show deleted lines on the left (but not added lines) and added lines on the right (but not deleted lines).

In comparison vscode/git/delta.. would never show added lines on the left pane (text with green bg) or deleted lines on the right pane (text with red bg).

[clason]

Then, no, that is not possible.