Support environment variables?

[Asya-kawai]

Description

• Does support environment variables that load parameters from environment variables instead of command line arguments?
• Environment variables support is useful when using depreq in pipeline of CI config file(like as yaml)

Change

In addition to support for command line argument, wish support environment variables as below.

GIT_USER=amaya382
depreq \
  : "load from environment variable --git-user amaya382" \
  --git-email mail@sapphire.in.net \
  --git-token <your-git-token> \
  --git-token-user amaya382 \
  --manifest-uri 'https://github.com/gitops-demo/manifests.git' \
  --manifest-base-branch dev \
  --manifest-values-files app-a/values/dev-app-a.yaml:app-a/values/prd-app-a.yaml \
  --manifest-tag-keys 'image.repository' \
  --app-image gitopsdemo/app-a \
  --app-curr-commit <commit-hash-from-ci> \
  --github-user amaya382

[amaya382]

It sounds good. Let me file this feature in the next release.

Note: Variables from env should be overridden by variables passed as a parameter