dgoss: Copy multiple files with GOSS_FILES_PATH

[dklimpel]

Describe the feature:

I would like to reuse tests for different container images and create a structure with tests. This should work well with the gossfile configuration. However, dgoss only copies a configuration and not an entire directory with the parameter GOSS_FILES_PATH.

Describe the solution you'd like

• Copy all files from GOSS_FILES_PATH, (Is this a breaking change?)
• copy whole directory if GOSS_FILES_PATH has not it's default value .
• add a new parameter, similar to -d like in kgoss, -d is already user by docker run
• new env variable with list of directories to copy

Maybe there are other solutions.

Related to:

• Make dgoss support gossfile directives #603
• update dgoss to support imported goss files #236