title: Where does pre-commit install "environments"?
body: <p>I'm trying to setup <a href="https://pre-commit.com/" rel="noreferrer"><code>pre-commit</code></a> for a Python project's repository. Upon running <code>pre-commit install</code> I see an output like this:</p>
  <pre><code>[INFO] Installing environment for https://github.com/asottile/seed-isort-config.
  [INFO] Once installed this environment will be reused.
  [INFO] This may take a few minutes...
  [INFO] Installing environment for https://github.com/pre-commit/mirrors-isort.
  [INFO] Once installed this environment will be reused.
  [INFO] This may take a few minutes...
  [INFO] Installing environment for https://github.com/pre-commit/pre-commit-hooks.
  [INFO] Once installed this environment will be reused.
  [INFO] This may take a few minutes...
  [INFO] Installing environment for https://github.com/pre-commit/mirrors-pylint.
  [INFO] Once installed this environment will be reused.
  [INFO] This may take a few minutes...
  </code></pre>
  <p>What are these &quot;environments&quot; and where are they being installed to?</p>