Re-post of angular/devkit#745

Bug Report or Feature Request (mark with an x)

- [x] bug report -> please search issues before submitting
- [ ] feature request

Area

- [ ] devkit
- [x] schematics

Versions

Node v8.11.1
NPM 5.8.0
Mac OS High Sierra

Repro steps

Use the following schematic

import { Rule, url, apply, mergeWith, chain, MergeStrategy } from '@angular-devkit/schematics';

export function index(): Rule {
  return chain([
    simpleMerge(),
  ]);
}

function simpleMerge(): Rule {

  const source = url('./files');

  return mergeWith(source, MergeStrategy.Overwrite);
}

The log given by the failure

schematics .:boilerplate

ERROR! /src/app/app.component.html already exists.
ERROR! /src/app/app.component.spec.ts already exists.
ERROR! /src/app/app.component.ts already exists.
ERROR! /src/app/app.module.ts already exists.
ERROR! /src/assets/.gitkeep already exists.
ERROR! /src/environments/environment.prod.ts already exists.
ERROR! /src/environments/environment.ts already exists.
ERROR! /src/index.html already exists.

Desired functionality

All files should be overwritten.

Mention any other details that might be useful

I tried every MergeStrategy possible (AllowOverwriteConflict, etc.), same result.

angular/devkit#745
https://stackoverflow.com/questions/48957132/how-to-overwrite-file-with-angular-schematics