Add sorting inventories function.

internal.lua

@@ -144,3 +144,48 @@ function unified_inventory.items_in_group(groups)
 	end
 	return items
 end
+
+function unified_inventory.sort_inventory(inv)
+	local inlist = inv:get_list("main")
+	local typecnt = {}
+	local typekeys = {}
+	for _, st in ipairs(inlist) do
+		if not st:is_empty() then
+			local n = st:get_name()
+			local w = st:get_wear()
+			local m = st:get_metadata()
+			local k = string.format("%s %05d %s", n, w, m)
+			if not typecnt[k] then
+				typecnt[k] = {
+					name = n,
+					wear = w,
+					metadata = m,
+					stack_max = st:get_stack_max(),
+					count = 0,
+				}
+				table.insert(typekeys, k)
+			end
+			typecnt[k].count = typecnt[k].count + st:get_count()
+		end
+	end
+	table.sort(typekeys)
+	local outlist = {}
+	for _, k in ipairs(typekeys) do
+		local tc = typecnt[k]
+		while tc.count > 0 do
+			local c = math.min(tc.count, tc.stack_max)
+			table.insert(outlist, ItemStack({
+				name = tc.name,
+				wear = tc.wear,
+				metadata = tc.metadata,
+				count = c,
+			}))
+			tc.count = tc.count - c
+		end
+	end
+	if #outlist > #inlist then return end
+	while #outlist < #inlist do
+		table.insert(outlist, ItemStack(nil))
+	end
+	inv:set_list("main", outlist)
+end