deb - stage files from .deb packages

Host dependencies:

• arpy (python package)

Usage:

# Specify the deb source kind
kind: deb

# Optionally specify a relative staging directory
# directory: path/to/stage

# Specify the deb url. Using an alias defined in your project
# configuration is encouraged. 'bst track' will update the
# sha256sum in 'ref' to the downloaded file's sha256sum.
url: upstream:foo.deb

# Specify the ref. It's a sha256sum of the file you download.
ref: 6c9f6f68a131ec6381da82f2bff978083ed7f4f7991d931bfa767b7965ebc94b

# Specify the basedir to return only the specified dir and it's children
base-dir: ''