Port human_time from Pepperminty Wiki & put it to use in //multi

Also, we've got a changelog!

CHANGELOG.md

@@ -0,0 +1,6 @@
+# WorldEditAdditions Changelog
+It's about time I started a changelog! This will serve from now on as the master changelog for WorldEditAdditions.
+
+
+## v1.8 (unreleased)
+ - Update `//multi` to display human readable times (e.g. `2.11mins` instead of `126600ms`)

worldeditadditions/utils/strings.lua

@@ -208,3 +208,30 @@ function worldeditadditions.parse_weighted_nodes(parts, as_list)
 	
 	return true, result
 end
+
+--- Converts a float milliseconds into a human-readable string.
+-- Ported from PHP human_time from Pepperminty Wiki: https://github.com/sbrl/Pepperminty-Wiki/blob/fa81f0d/core/05-functions.php#L82-L104
+-- @param	ms		float	The number of milliseconds to convert.
+-- @return	string	A human-readable string representing the input ms.
+function worldeditadditions.human_time(ms)
+	local tokens = {
+		{ 31536000 * 1000, 'year' },
+		{ 2592000 * 1000, 'month' },
+		{ 604800 * 1000, 'week' },
+		{ 86400 * 1000, 'day' },
+		{ 3600 * 1000, 'hr' },
+		{ 60 * 1000, 'min' },
+		{ 1 * 1000, 's' },
+		{ 1, 'ms'}
+	}
+	
+	for _,pair in pairs(tokens) do
+		if ms > pair[1] or pair[2] == "ms" then
+			local unit = pair[2]
+			if ms > 60 * 1000 and math.floor(ms / pair[1]) > 1 then
+				unit = unit.."s"
+			end
+			return string.format("%.2f", ms / pair[1])..unit
+		end
+	end
+end

worldeditadditions_commands/multi.lua

@@ -66,12 +66,20 @@ minetest.register_chatcommand("/multi", {
 		end
 		
 		local total_time = (os.clock() - master_start_time) * 1000
-		local done_message = string.format("Executed %d commands in %.2fms (", #times, total_time)
+		local done_message = {}
+		table.insert(done_message,
+			string.format("Executed %d commands in %s (",
+				#times,
+				worldeditadditions.human_time(total_time)
+			)
+		)
+		local message_parts = {}
 		for j=1,#times do
-			done_message = done_message..string.format("%.2fms, ", times[j])
+			table.insert(message_parts, worldeditadditions.human_time(times[j]))
 		end
-		done_message = string.sub(done_message, 0, string.len(done_message) - 2)..")"
+		table.insert(done_message, table.concat(message_parts, ", "))
+		table.insert(done_message, ")")
 		
-		worldedit.player_notify(name, done_message)
+		worldedit.player_notify(name, table.concat(done_message, ""))
 	end
 })