Move toPromise to its own file

src/manager.ts

@@ -2,6 +2,7 @@
 import { Client, ConnectConfig } from 'ssh2';
 import * as vscode from 'vscode';
 import SSHFileSystem, { EMPTY_FILE_SYSTEM } from './sshFileSystem';
+import { toPromise } from './toPromise';
 
 async function assertFs(man: Manager, uri: vscode.Uri) {
   const fs = await man.getFs(uri);

src/sshFileSystem.ts

@@ -4,12 +4,7 @@ import * as ssh2 from 'ssh2';
 import * as ssh2s from 'ssh2-streams';
 import * as vscode from 'vscode';
 
-type toPromiseCallback<T> = (err: Error | null, res?: T) => void;
-async function toPromise<T>(func: (cb: toPromiseCallback<T>) => void): Promise<T> {
-  return new Promise<T>((resolve, reject) => {
-    func((err, res) => err ? reject(err) : resolve(res));
-  });
-}
+import { toPromise } from './toPromise';
 
 export class SSHFileSystem implements vscode.FileSystemProvider {
   public copy = undefined;

src/toPromise.ts

@@ -0,0 +1,7 @@
+
+export type toPromiseCallback<T> = (err: Error | null, res?: T) => void;
+export async function toPromise<T>(func: (cb: toPromiseCallback<T>) => void): Promise<T> {
+  return new Promise<T>((resolve, reject) => {
+    func((err, res) => err ? reject(err) : resolve(res));
+  });
+}