feat(git): show staged hunks in the gutter with a stage toggle

plugin/git.lua

@@ -41,12 +41,47 @@ local DEFAULT_HIGHLIGHTS = {
     GitHunkAddLine = "DiffAdd",
     GitHunkDeleteLine = "DiffDelete",
 }
-for name, link in pairs(DEFAULT_HIGHLIGHTS) do
-    vim.api.nvim_set_hl(0, name, { link = link, default = true })
+local STAGED_HUNK_HL = {
+    GitHunkStagedAdded = "GitHunkAdded",
+    GitHunkStagedChanged = "GitHunkChanged",
+    GitHunkStagedRemoved = "GitHunkRemoved",
+}
+
+local function blend(a, b, t)
+    local function mix(shift)
+        local x = bit.band(bit.rshift(a, shift), 0xff)
+        local y = bit.band(bit.rshift(b, shift), 0xff)
+        return bit.lshift(math.floor(x + (y - x) * t + 0.5), shift)
+    end
+    return mix(16) + mix(8) + mix(0)
 end
 
+local function apply_highlights()
+    for name, link in pairs(DEFAULT_HIGHLIGHTS) do
+        vim.api.nvim_set_hl(0, name, { link = link, default = true })
+    end
+    local bg = vim.api.nvim_get_hl(0, { name = "Normal" }).bg or 0x000000
+    for name, base in pairs(STAGED_HUNK_HL) do
+        local src = vim.api.nvim_get_hl(0, { name = base, link = false })
+        local hl = {}
+        if src.fg then
+            hl.fg = blend(src.fg, bg, 0.45)
+        end
+        if src.bg then
+            hl.bg = blend(src.bg, bg, 0.45)
+        end
+        vim.api.nvim_set_hl(0, name, hl)
+    end
+end
+apply_highlights()
+
 local group = vim.api.nvim_create_augroup("ow.git", { clear = true })
 
+vim.api.nvim_create_autocmd("ColorScheme", {
+    group = group,
+    callback = apply_highlights,
+})
+
 vim.api.nvim_create_autocmd({ "BufReadPost", "BufNewFile" }, {
     group = group,
     callback = function(args)
@@ -262,7 +297,7 @@ vim.keymap.set({ "n", "x" }, "<Plug>(git-hunk-prev)", function()
 end, { silent = true, desc = "Jump to previous git hunk" })
 vim.keymap.set("n", "<Plug>(git-hunk-stage)", function()
     require("git.hunks").stage_hunk()
-end, { silent = true, desc = "Stage hunk under cursor" })
+end, { silent = true, desc = "Stage or unstage the hunk under cursor" })
 vim.keymap.set("n", "<Plug>(git-hunk-reset)", function()
     require("git.hunks").reset_hunk()
 end, { silent = true, desc = "Reset hunk under cursor" })