title: lint-staged is running ng -lint for all the changed files instead of only staged files
body: <p>I am trying to use husky with lint-staged for pre commit git hooks in angular5. Prettier formats only the staged files. But when I run ng lint command it runs on all the changed files instead of running on only staged files(I have 4 files modified, but only 2 files added to staging area using git add command. But all 4 files are checked for linting which is not what I expect)</p>
  
  <p>Here is the configuration in .lintstagedrc</p>
  
  <pre><code>  "*.{ts,json}": [
      "prettier --write",
      "ng lint myProjName --files",
      "git add"
    ],
    "*.less": [
      "prettier --write",
      "npm run stylelint",
      "git add"
    ]
  }```
  
  I debugged the issue to some extent. --files takes only the files which have been staged into the account. But still when the linters task completes, I get errors for non staged files as well.
  </code></pre>