chore(fs): simplify sync/forget

- These methods are now optional
- sync no longer returns anything

@xen-orchestra/fs/src/abstract.js

@@ -283,8 +283,8 @@ export default class RemoteHandlerAbstract {
 
   // Asks the handler to sync the state of the effective remote with its'
   // metadata
-  async sync(): Promise<mixed> {
-    return this._sync()
+  async sync(): Promise<void> {
+    await this._sync()
   }
 
   async test(): Promise<Object> {
@@ -340,9 +340,8 @@ export default class RemoteHandlerAbstract {
     throw new Error('Not implemented')
   }
 
-  async _forget(): Promise<void> {
-    throw new Error('Not implemented')
-  }
+  // called to finalize the remote
+  async _forget(): Promise<void> {}
 
   async _getSize(file: File): Promise<number> {
     throw new Error('Not implemented')
@@ -404,9 +403,8 @@ export default class RemoteHandlerAbstract {
     return this._rmtree(dir)
   }
 
-  async _sync(): Promise<mixed> {
-    throw new Error('Not implemented')
-  }
+  // called to initialize the remote
+  async _sync(): Promise<void> {}
 
   async _unlink(file: string): Promise<void> {
     throw new Error('Not implemented')

@xen-orchestra/fs/src/local.js

@@ -1,6 +1,5 @@
 import fs from 'fs-extra'
 import { dirname } from 'path'
-import { noop } from 'lodash'
 
 import RemoteHandlerAbstract from './abstract'
 
@@ -44,10 +43,6 @@ export default class LocalHandler extends RemoteHandlerAbstract {
         })
   }
 
-  async _forget() {
-    return noop()
-  }
-
   async _getSize(file) {
     const stats = await fs.stat(
       this._getFilePath(typeof file === 'string' ? file : file.path)
@@ -100,11 +95,9 @@ export default class LocalHandler extends RemoteHandlerAbstract {
   }
 
   async _sync() {
-    const path = this._getRealPath()
+    const path = this._getRealPath('/')
     await fs.ensureDir(path)
     await fs.access(path, fs.R_OK | fs.W_OK)
-
-    return this._remote
   }
 
   async _unlink(file) {

@xen-orchestra/fs/src/smb.js

@@ -4,8 +4,6 @@ import { finished } from 'readable-stream'
 
 import RemoteHandlerAbstract from './abstract'
 
-const noop = () => {}
-
 // Normalize the error code for file not found.
 const wrapError = (error, code) => ({
   __proto__: error,
@@ -30,7 +28,6 @@ const normalizeError = (error, shouldBeDirectory) => {
 export default class SmbHandler extends RemoteHandlerAbstract {
   constructor(remote, opts) {
     super(remote, opts)
-    this._forget = noop
 
     const prefix = this._remote.path
     this._prefix = prefix !== '' ? prefix + '\\' : prefix
@@ -228,8 +225,6 @@ export default class SmbHandler extends RemoteHandlerAbstract {
   async _sync() {
     // Check access (smb2 does not expose connect in public so far...)
     await this.list('.')
-
-    return this._remote
   }
 
   async _unlink(file) {