title: Package updates from remote git repository are not reflected in site-packages
body: <p>I have been trying to upgrade a package based off of the most recent changes on git but the changes aren't taking effect. I ran several variations of this command, such as also using <code>python -m pip</code> and the actual path to the pip version in anaconda, as well as adding --upgrade: <code>pip install git+git://github.com/lmcinnes/umap@master</code></p>
  <p>Here is the output each time:</p>
  <pre><code>Collecting git+git://github.com/lmcinnes/umap@master
    Cloning git://github.com/lmcinnes/umap (to revision master) to /tmp/pip-req-build-bck1u0of
    Running command git clone -q git://github.com/lmcinnes/umap /tmp/pip-req-build-bck1u0of
  Requirement already satisfied: numpy&gt;=1.17 in /home/himani/anaconda3/lib/python3.7/site-packages (from umap-learn==0.5.1) (1.19.2)
  Requirement already satisfied: scikit-learn&gt;=0.22 in /home/himani/anaconda3/lib/python3.7/site-packages (from umap-learn==0.5.1) (0.23.2)
  Requirement already satisfied: scipy&gt;=1.0 in /home/himani/anaconda3/lib/python3.7/site-packages (from umap-learn==0.5.1) (1.6.0)
  Requirement already satisfied: numba&gt;=0.49 in /home/himani/anaconda3/lib/python3.7/site-packages (from umap-learn==0.5.1) (0.51.2)
  Requirement already satisfied: pynndescent&gt;=0.5 in /home/himani/anaconda3/lib/python3.7/site-packages (from umap-learn==0.5.1) (0.5.2)
  Requirement already satisfied: llvmlite&lt;0.35,&gt;=0.34.0.dev0 in /home/himani/anaconda3/lib/python3.7/site-packages (from numba&gt;=0.49-&gt;umap-learn==0.5.1) (0.34.0)
  Requirement already satisfied: setuptools in /home/himani/anaconda3/lib/python3.7/site-packages (from numba&gt;=0.49-&gt;umap-learn==0.5.1) (52.0.0.post20210125)
  Requirement already satisfied: joblib&gt;=0.11 in /home/himani/anaconda3/lib/python3.7/site-packages (from pynndescent&gt;=0.5-&gt;umap-learn==0.5.1) (1.0.0)
  Requirement already satisfied: threadpoolctl&gt;=2.0.0 in /home/himani/anaconda3/lib/python3.7/site-packages (from scikit-learn&gt;=0.22-&gt;umap-learn==0.5.1) (2.1.0)
  </code></pre>
  <p>And looking in the actual directory of where umap is in site-packages, I can see that none of the files are being changed to reflect the updates, so it seems that nothing is happening. I am tempted to just manually change the files myself but I know that wouldn't be smart for the long run.</p>