supporting environment.yml updates

[fdosani]

@ak-gupta thoughts on adding in support for updating environment.yml based on feedback from @ryanSoley. This I think could fit in nicely with the conda plugin?

[ak-gupta]

Hm, I think we have a couple options here:

1. edgetest: We can add a CLI option like --additional-files that specifies a list of files beyond setup.cfg/requirements.txt to update. In this case we would need to add some YAML handling to make sure we handle the updates correctly.
2. edgetest-conda: We can add the ability for users to create the test environments from a YAML (instead of specifying conda dependencies). After that, we can add a post-run hook to update the supplied YAML.

The biggest issue with these solutions is that we don't have a great way to verify that the updated pins will work with the YAML. For example, a package might have a broken conda-forge pipeline, but their package publishes successfully to PyPI.

[fdosani]

Looking into this a bit more. I think I like keeping this in the conda plugin since it seems very specific to that.

Maybe another flag being added to denote updating a environment.yml or meta.yml and executing some post-hook seems to a simple path forward.

[fdosani]

@ak-gupta Thought on this solution for environment.yml. We just go through the motions of upgrading and then just export as a post hook?

So equivalent to: conda env export > environment.yml. This seems like a really LoE and easy way to update the environment using built in conda functionality. @ryanSoley thoughts on this?

[fdosani]

This is a long standing issue. Will take a stab at a working PoC in the next couple of weeks. Along with #29