Managing Custom ISIS3 Dependencies (WIP)

The ISIS Conda Environment

TODO:
* what is conda?
* what is anaconda.org?
* what are "channels"
* Do we describe these things here or link to external documentation?

The third-party dependencies required to build and run ISIS3 versions 3.6.0 and above are specified in the [environment.yml](https://github.com/USGS-Astrogeology/ISIS3/blob/cmake/environment.yml) file located at the root of the ISIS3 repo. For more info on editing a conda environment file, view the [Conda Documentation](https://conda.io/docs/user-guide/tasks/manage-environments.html)

Most of the packages listed in the file are pulled from conda-forge, but there are a few custom builds that we have uploaded to [usgs-astrogeology](https://anaconda.org/usgs-astrogeology/repo), such as qt. The recipes to build and upload these packages can be found on the [isis3_dependencies](https://github.com/USGS-Astrogeology/isis3_dependencies) repo.

# Environment Setup

1. [Download and install the latest version of Anaconda](https://www.anaconda.com/download).
1. Fork and clone the [isis3_dependencies repo](https://github.com/usgs-astrogeology/isis3_depenedencies).
1. Change directory into the isis3_dependencies clone (e.g. ```cd isis3_dependencies```)
1. Add the conda-forge and usgs-astrogeology anaconda.org channels to your anaconda configuration:
  ```bash
  conda config --add channels conda-forge --add channels usgs-astrogeology

Important files in the isis3_dependencies repo

There are three directories in the isis3_dependencies repo: bin/, meta/, and recipies/.

The bin/ directory contains some python scripts that are used for determining dependencies and available packages, as well as a script for building packages. The build_package.py script is the script we will use to build a package for uploading to the USGS-Astrogeology anaconda.org cloud.

The meta/ directory contains

The recipies/ directory contains

For more information on how conda builds work, see the Conda build recipes documentation.

Using the Anaconda Upload Python Scripts

To build and upload a package to anaconda, run python bin/build_package.py <package> from the root of the isis_dependencies repo. This requires you to log into an anaconda account with write permissions for the usgs-astrogeology repo. This command will use the build.sh script and meta.yaml specifications found in the recipies/ directory. If there is no meta.yaml file, but a meta.yaml.tmpl file exists, one will be created using the template.

Building some of the packages will require conda-forge and usgs-astrogeolgy to be in your channels, so add them with conda config --add channels conda-forge --add channels usgs-astrogeology