title: Is Poetry install the package when we do poetry add?
body: <p>I'm new to Poetry, and somehow, reading the doc on the web does not really help me to understand about this tool.
  So, i have existing project without using Poetry and i want to write <code>pyproject.toml</code> and <code>poetry.lock</code> files using <code>requirements.txt</code> from pip, to make other people easier to produce my result. For this, i use command:</p>
  <blockquote>
  <p>poetry add 'cat requirements.txt'</p>
  </blockquote>
  <p>But when the command is running, it seems like Poetry is installing the package again. Can anyone explain to me about this? Thank you</p>
  <p>Here is the command result:</p>
  <pre><code>$ poetry add `cat requirements.txt`
  Using version ^1.21.2 for numpy
  Using version ^0.46 for olefile
  Using version ^8.3.2 for Pillow
  Using version ^3.10.0 for typing-extensions
  
  Updating dependencies
  Resolving dependencies...
  
  Writing lock file
  
  Package operations: 35 installs, 0 updates, 0 removals
  
    • Installing colorama (0.4.4)
    • Installing catalogue (2.0.6)
    • Installing click (8.0.3)
    • Installing cymem (2.0.5)
    • Installing numpy (1.21.2)
    • Installing typing-extensions (3.10.0.2)
    • Installing blis (0.7.4)
    • Installing certifi (2021.10.8)
    • Installing charset-normalizer (2.0.7)
    • Installing idna (3.2)
    • Installing preshed (3.0.5)
    • Installing smart-open (5.2.1)
    • Installing srsly (2.4.1)
    • Installing pyparsing (2.4.7)
    • Installing pydantic (1.8.2)
    • Installing urllib3 (1.26.7)
    • Installing typer (0.4.0)
    • Installing wasabi (0.8.2)
    • Installing markupsafe (2.0.1)
    • Installing fastrlock (0.6)
    • Installing packaging (21.0)
    • Installing pathy (0.6.0)
    • Installing jinja2 (3.0.2)
    • Installing spacy-legacy (3.0.8)
    • Installing torch (1.8.0)
    • Installing thinc (8.0.10)
    • Installing tqdm (4.62.3)
    • Installing pillow (8.3.2)
    • Installing requests (2.26.0)
    • Installing cupy-cuda111 (9.5.0)
    • Installing olefile (0.46)
    • Installing torchtext (0.9.0)
    • Installing spacy (3.1.3)
    • Installing torchvision (0.9.0)
    • Installing torchaudio (0.8.0)
  </code></pre>