Fix NeoTree diagnostic signs background by adding NeoTreeSignColumn config

Co-authored-by: ellisonleao <[email protected]>

Author: Copilot

lua/gruvbox.lua

@@ -1131,6 +1131,7 @@ local function get_groups()
     NeoTreeTitleBar = { fg = colors.fg1, bg = colors.bg2 },
     NeoTreeDirectoryIcon = { link = "GruvboxGreen" },
     NeoTreeDirectoryName = { link = "GruvboxGreenBold" },
+    NeoTreeSignColumn = { bg = "NONE" },
     ["@comment"] = { link = "Comment" },
     ["@none"] = { bg = "NONE", fg = "NONE" },
     ["@preproc"] = { link = "PreProc" },

tests/gruvbox/gruvbox_spec.lua

@@ -186,4 +186,19 @@ describe("tests", function()
     assert.are.same(gruvbox.config.contrast, "")
     assert.is_nil(gruvbox.config.overrides.Normal)
   end)
+
+  it("should set NeoTreeSignColumn background to NONE", function()
+    gruvbox.setup()
+    gruvbox.load()
+
+    local group_id = vim.api.nvim_get_hl_id_by_name("NeoTreeSignColumn")
+    local values = {
+      bg = vim.fn.synIDattr(group_id, "bg", "gui"),
+    }
+
+    local expected = {
+      bg = "",  -- "NONE" translates to empty string in synIDattr
+    }
+    assert.are.same(expected, values)
+  end)
 end)