add fs.flush() that saves superblock

Author: jcubic

src/DefaultBackend.js

@@ -13,7 +13,7 @@ const path = require("./path.js");
 module.exports = class DefaultBackend {
   constructor() {
     this.saveSuperblock = debounce(() => {
-      this._saveSuperblock();
+      this.flush();
     }, 500);
   }
   async init (name, {
@@ -180,4 +180,7 @@ module.exports = class DefaultBackend {
   du(filepath) {
     return this._cache.du(filepath);
   }
+  flush() {
+    return this._saveSuperblock();
+  }
 }

src/PromisifiedFS.js

@@ -198,4 +198,7 @@ module.exports = class PromisifiedFS {
   async du(filepath) {
     return this._backend.du(filepath);
   }
+  async flush() {
+    return this._backend.flush();
+  }
 }

src/index.js

@@ -29,6 +29,7 @@ module.exports = class FS {
     this.symlink = this.symlink.bind(this)
     this.backFile = this.backFile.bind(this)
     this.du = this.du.bind(this)
+    this.flush = this.flush.bind(this)
   }
   init(name, options) {
     return this.promises.init(name, options)
@@ -85,4 +86,8 @@ module.exports = class FS {
     const [resolve, reject] = wrapCallback(cb);
     this.promises.du(filepath).then(resolve).catch(reject);
   }
+  flush(cb) {
+    const [resolve, reject] = wrapCallback(cb);
+    this.promises.flush().then(resolve).catch(reject);
+  }
 }