Fix the CI failing issue on Hexo (#27)

* Revert "Reduce scope such as recursive function"

* Update fs.js

* Update fs.js

lib/fs.js

@@ -447,13 +447,20 @@ function watch(path, options, callback) {
 function _findUnusedPath(path, files) {
   const ext = extname(path);
   const base = basename(path, ext);
-  const regex = new RegExp(`^${escapeRegExp(base)}-(\\d+)${escapeRegExp(ext)}$`);
+  const regex = new RegExp(`^${escapeRegExp(base)}(?:-(\\d+))?${escapeRegExp(ext)}$`);
+  let num = -1;
 
-  const num = files.reduce((_num, item) => {
-    const match = regex.exec(item);
+  for (let i = 0, len = files.length; i < len; i++) {
+    const item = files[i];
+    if (!regex.test(item)) continue;
+
+    const match = item.match(regex);
+    const matchNum = match[1] ? parseInt(match[1], 10) : 0;
 
-    return match != null ? Math.max(parseInt(match[1], 10), _num) : _num;
-  }, -1);
+    if (matchNum > num) {
+      num = matchNum;
+    }
+  }
 
   return join(dirname(path), `${base}-${num + 1}${ext}`);
 }