refactor: ANSI colorize continuous chunks at once

- This improves the speed.
- If not done, for large diffs we can get the error `PANIC: unprotected error in call to Lua API (EMFILE: too many open files)`.

Author: stevenxxiu

lua/neogit/lib/buffer.lua

@@ -139,21 +139,38 @@ function Buffer:set_extmarks(extmarks)
 end
 
 function Buffer:set_line_highlights(highlights)
-  local line_ansi_colorized = {}
+  local line_ansi_colorized_map = {}
 
   for _, hl in ipairs(highlights) do
     local line_nr, hl_group = unpack(hl)
     if hl_group == "NeogitDiffContext" then
-      if not line_ansi_colorized[line_nr] then
-        local text = self:get_line(line_nr + 1)
-        vim.g.baleia.buf_set_lines(self.handle, line_nr, line_nr + 1, false, text)
-        line_ansi_colorized[line_nr] = true
-      end
+      line_ansi_colorized_map[line_nr] = true
+    else
+      self:add_line_highlight(unpack(hl))
     end
+  end
 
-    if not line_ansi_colorized[line_nr] then
-      self:add_line_highlight(unpack(hl))
+  local line_ansi_colorized = {}
+  for k in pairs(line_ansi_colorized_map) do
+    table.insert(line_ansi_colorized, k)
+  end
+  table.sort(line_ansi_colorized)
+
+  local start_line_nr, prev_line_nr
+  for _, line_nr in ipairs(line_ansi_colorized) do
+    if start_line_nr == nil then
+      start_line_nr = line_nr
     end
+    if prev_line_nr ~= nil and line_nr ~= prev_line_nr + 1 then
+      local text = self:get_lines(start_line_nr, prev_line_nr + 1, false)
+      vim.g.baleia.buf_set_lines(self.handle, start_line_nr, prev_line_nr + 1, false, text)
+      start_line_nr = line_nr
+    end
+    prev_line_nr = line_nr
+  end
+  if start_line_nr ~= nil then
+    local text = self:get_lines(start_line_nr, prev_line_nr + 1, false)
+    vim.g.baleia.buf_set_lines(self.handle, start_line_nr, prev_line_nr + 1, false, text)
   end
 end