Add initial support for sindrets/diffview.nvim

[przepompownia]

At this moment it only changes highlights for file history panel.

[przepompownia]

Before:

After:

[przepompownia]

For diff content diffview.nvim uses built-in highlight groups (DiffviewDiffAdd links to DiffAdd etc.). @gbprod what do you think about change Diff* to something more subtle? Currently built-in diff view looks like above:

[gbprod]

Hi @przepompownia, thanks for this PR, it seems nice.

What are you thinking about when you say something more subtle ?
You can configure diff colors using diff.mode option (I think that it looks better with the fg value :) )

[przepompownia]

Hi @gbprod, I mean colors that stand out less from the palette. I have no suggestion at the moment.

diff = { mode = 'fg'} looks nice for me, but mixes with treesitter highlights:

but after

diff --git a/lua/nord/utils/init.lua b/lua/nord/utils/init.lua
index d6a4c5a..30585c3 100644
--- a/lua/nord/utils/init.lua
+++ b/lua/nord/utils/init.lua
@@ -13,7 +13,7 @@ end
 function utils.make_diff(color)
   local options = require("nord.config").options
 
-  return { fg = color, bg = c.none, reverse = options.diff.mode ~= "fg" }
+  return { fg = color, bg = c.polar_night.brighter, reverse = options.diff.mode ~= "fg" }
 end

diff.mode = fg looks more readable for me

and the default mode seems to be unchanged:

[gbprod]

Nice!
Can you create a PR with this change?

[przepompownia]

Thanks for merging. Starting to look for practical use of this tool for myself I focused on file history panel only.

Nice! Can you create a PR with this change?

#37