Support some common conda-based workflows

[bollwyvl]

Elevator Pitch

Offer some additional declarative support for using conda-based tools in doitomlworkflows without adding any hard dependencies, such as with a doitoml[conda].

Motivation

Doit works fairly well with conda (given an outer environment with python and doit), but leads to a lot of boilerplate.

Design Ideas

flowchart TB
    partial.env.yml -- inherit_from --> another.env.yml
    partial.env.yml -- conda-lock --> lock.yml --> lock.txt
    partial.env.yml --> environment.yml --> readthedocs.org & mybinder.org 
    lock.txt -- create --> prefix/conda-meta/history
    prefix/conda-meta/history --> conda-run --> actions
    lock.txt -- environment_file --> construct.yml --> installer.sh & installer.exe & installer.pkg
    meta.yaml -- conda build --> package.conda
    recipe.yaml -- boa build --> package.conda
    package.conda --> construct.yml

• build conda.lock.txt files from environment.yml files, with support for
  • declarative multiple inheritance of yaml files
  • solve matrices with multiple factors (with punch-out)
  • platform-specific dependencies
• build portable environment.yml for consumption on e.g.
  • readthedocs.org
  • mybinder.org
• creating conda environments
  • selecting/provisioning $CONDA_EXE
• modifying actions with [conda, run, --prefix, "{prefix}", --no-capture-output]
• build constructor installers from construct.yaml
• build .conda packages from meta.yaml and recipe.yaml

Prior art

• jupyterlab-fonts
  • requires a preflight to pre-calculate some values, which is undesirable