title: How to prevent 'conda env export' from updating specific dependencies
body: <p>Here's an excerpt from my <code>environment.yml</code>:</p>
  <pre><code>name: my-project
  channels:
    - pytorch-nightly
    - defaults
  dependencies:
    - pytorch=1.13.0.*
    - pip:
      - https://github.com/explosion/spacy-models/releases/download/nb_core_news_md-3.3.0/nb_core_news_md-3.3.0-py3-none-any.whl
  prefix: ~/opt/miniconda3/envs/my-project
  </code></pre>
  <p>When I create my environment (<code>conda env create -f environment.yml</code>) and re-export it to <code>environment.yml</code> (<code>conda env export &gt; environment.yml</code>), the file gets changed:</p>
  <pre><code>name: my-project
  channels:
    - pytorch-nightly
    - defaults
  dependencies:
    - pytorch=1.13.0.dev20220614=py3.9_0
    - pip:
      - nb-core-news-md==3.3.0
  prefix: ~/opt/miniconda3/envs/my-project
  </code></pre>
  <p>Then, when I re-create my environment the next day, Conda complains that <code>pytorch=1.13.0.dev20220614=py3.9_0</code> does not exist because it was replaced by a new PyTorch Preview (Nightly) build. <code>dev20220614=py3.9_0</code> is no longer available.</p>
  <p>Conda also complains that <code>nb-core-news-md==3.3.0</code> does not exist. It was installed via a URL directly to the <code>whl</code>. That URL was removed from the <code>environment.yml</code>.</p>
  <p>How can I prevent <code>conda env export</code> from changing these two dependencies? I still want Conda to lock down the specifics for all other dependencies, just not for these two.</p>