fix: support natural ordering for numbers with >12 digits (#652)

* fix: support natural ordering for numbers with >12 digits

Changes the column ordering code when `view_options.natural_order`
is enabled, so that it can support larger numbers.

The previous 12-digit padding approach breaks for numbers above 12
digits.

This length-prefixed approach can scale to much higher numbers.
I picked %03 (padding 3 digits) because most filesystems don't allow
more than 255 bytes in a path segment, and "255" is 3 digits long.

* add memoization to natural order sorting

* remove call to unpack

Author: XeroOl

lua/oil/columns.lua

@@ -228,8 +228,8 @@ M.register("type", {
   end,
 })
 
-local function pad_number(int)
-  return string.format("%012d", int)
+local function adjust_number(int)
+  return string.format("%03d%s", #int, int)
 end
 
 M.register("name", {
@@ -256,14 +256,16 @@ M.register("name", {
         end
       end
     else
-      if config.view_options.case_insensitive then
-        return function(entry)
-          return entry[FIELD_NAME]:gsub("%d+", pad_number):lower()
-        end
-      else
-        return function(entry)
-          return entry[FIELD_NAME]:gsub("%d+", pad_number)
+      local memo = {}
+      return function(entry)
+        if memo[entry] == nil then
+          local name = entry[FIELD_NAME]:gsub("0*(%d+)", adjust_number)
+          if config.view_options.case_insensitive then
+            name = name:lower()
+          end
+          memo[entry] = name
         end
+        return memo[entry]
       end
     end
   end,

lua/oil/view.lua

@@ -587,7 +587,7 @@ local function get_sort_function(adapter, num_entries)
   end
   return function(a, b)
     for _, sort_fn in ipairs(idx_funs) do
-      local get_sort_value, order = unpack(sort_fn)
+      local get_sort_value, order = sort_fn[1], sort_fn[2]
       local a_val = get_sort_value(a)
       local b_val = get_sort_value(b)
       if a_val ~= b_val then