Md5 hash diffing to skip generating unchanged files (#316)

* add simple md5 hashing to compare file contents and speed up parsing

fix the import paths

* generate run.n

* output the hashes into cfg.outputDir + "/hashes/" instead of in the input directory

* generate run.n

src/dox/Dox.hx

@@ -138,7 +138,25 @@ class Dox {
 		function parseFile(path) {
 			var name = new Path(path).file;
 			Sys.println('Parsing $path');
+
+			var hashPaths = cfg.outputPath + "/hashes/";
+
+			if (!FileSystem.exists(hashPaths))
+				FileSystem.createDirectory(hashPaths);
+
 			var data = sys.io.File.getContent(path);
+			var md5Hash = haxe.crypto.Md5.encode(data);
+
+			if (sys.FileSystem.exists(hashPaths + name + ".md5")) {
+				var previousHash = sys.io.File.getContent(hashPaths + name + ".md5");
+				if (md5Hash == previousHash) {
+					Sys.println('Skipping $path, no file changes detected');
+					return;
+				}
+			}
+
+			sys.io.File.saveContent(hashPaths + name + ".md5", md5Hash);
+
 			var xml = try Xml.parse(data).firstElement() catch (err:Dynamic) {
 				trace('Error while parsing $path');
 				throw err;