Adding Dockerfile Parser

[vsoch]

This PR will serve to add a command line and programmatic (Python) way to convert from a Dockerfile to a SIngularity Recipe. To provide the reviewer with documentation and notes that are easier to read, please see the rendered docs on the Github pages from the vsoch branch of the equivalent repository:

https://vsoch.github.io/singularity-cli/recipes

We will need lots of help testing! Specifically, there are a lot of different formats / options that might go into a Dockerfile, and I only tested a very limited set. To help with this review, please do the following:

Install from vsoch master

git clone https://www.github.com/vsoch/singularity-cli
cd singularity-cli
python setup.py install

The above will place an executable spython in your local bin. The functions you import are from this module. See the documentation (next) for more details.

Documentation

Read the documentation and likely it will be easiest to test via the command line first. Then you have a few options. You can:

• Report issues here! I can address and update the vsoch/master branch, and then alert you when it's ready for re-test. or
• even better submit a tiny PR to the vsoch/master directly, it will be added here when it's merged.

Once you are happy with general recipe parsing, please continue to test the (from within python) functions.

Notes

• I have not yet written the logic to go back from a Singularity Recipe to Dockerfile... this will follow when I can do some more dinosaur programming!
• testing / CI would be greatly appreciated!

[vsoch]

This will close #5 and note that the Singularity --> Dockerfile parser should be developed in parallel!

[vsoch]

Singularity --> Dockerfile has been added, review away!

[vsoch]

Recipes to debug and test:

• https://github.com/CentOS/sig-cloud-instance-images/blob/CentOS-5/docker/Dockerfile