Overwriting git dependency with plain version dependency produces incorrect yaml

[seaneagan]

initial yaml:

dependencies:
  git: https://github.com/seaneagan/prompt.git

After running den install prompt:

dependencies:
  prompt:null

[Andersmholmgren]

This does look like the issue I hit. My use case is changing the types of dependencies. e.g. path <-> git and potentially hosted in the future