Track timestamps to filter changed files. (#500)

* Track timestamps to filter changed files.
* Regenerate test data

src/interfaces.ts

@@ -151,6 +151,7 @@ export interface WebpackNodeWatchFileSystem {
 
 export interface WebpackWatching {
     compiler: WebpackCompiler; // a guess
+    startTime: number;
 }
 
 export interface Resolve {

src/watch-run.ts

@@ -9,16 +9,23 @@ import constants = require('./constants');
 function makeWatchRun(
     instance: interfaces.TSInstance
 ) {
+    const lastTimes = {};
+    let startTime : number = null;
     return (watching: interfaces.WebpackWatching, cb: () => void) => {
         const watcher = watching.compiler.watchFileSystem.watcher ||
             watching.compiler.watchFileSystem.wfs.watcher;
         if (null === instance.modifiedFiles) {
             instance.modifiedFiles = {};
         }
-
-        Object.keys(watcher.getTimes())
-            .filter(filePath => !!filePath.match(constants.tsTsxJsJsxRegex))
+        startTime = startTime || watching.startTime;
+        const times = watcher.getTimes();
+        Object.keys(times)
+            .filter(filePath =>
+                times[filePath] > (lastTimes[filePath] || startTime)
+                && !!filePath.match(constants.tsTsxJsJsxRegex)
+            )
             .forEach(filePath => {
+                lastTimes[filePath] = times[filePath];
                 filePath = path.normalize(filePath);
                 const file = instance.files[filePath];
                 if (file) {