grim/convey

Clean up error handling the script/shell and add some unit tests
environment:
- VERSION=1.2.3
tasks:
script:
type: docker/run
image: alpine:edge
script:
- 'echo version: ${VERSION}'
- 'echo special: ${SPECIAL}'
- 'echo git commit: ${GIT_COMMIT}'
- 'echo hg commit: ${HG_COMMIT}'
environment:
- SPECIAL=true
plans:
default:
stages:
- tasks:
- script