Read from META.json and more

[perlpunk]

Summary:

• Add a Dockerfile with everything necessary to run cpanspec
• Add reading several things from META.json (dependencies, dynamic_config, provides)
• Skip parsing the code if provides exists in META.(json|yaml)
• Skip calling Makefile.PL etc. if dynamic_config exists in META.(json|yaml) and is false
• Move the code to call Makefile.PL etc. into it's own subprocessto avoid influencing the result
• Fix a case where the root directory of cpanspec was added to @INC and a Build.PL of a module was calling require "Makefile.PL" effectively calling cpanspec/Makefile.pL
• Add statistics output
• Add a script for batch processing a list of packages

Issue: https://progress.opensuse.org/issues/90047, #21

[perlpunk]

Example statistics output:

# STATS # # JSON::Validator, 4.17
# STATS # ---
# STATS # abstract:
# STATS #   metajson: Validate data against a JSON schema
# STATS #   metayaml: Validate data against a JSON schema
# STATS # dynamic: 0
# STATS # got_prereqs: 1
# STATS # license:
# STATS #   metajson:
# STATS #   - artistic_2
# STATS #   metayaml: artistic_2
# STATS #   spec: Artistic-2.0
# STATS # metajson: 1
# STATS # metayaml: 1
# STATS # name: JSON::Validator
# STATS # provides: 0
# STATS # summary: Validate data against a JSON schema
# STATS # version: '4.17'

So the logs can easily be analyzed with this:

% perl -nwlE'if (s/^# STATS # //) { print }' logfile
# Outputs list of YAML documents which can be loaded in perl or other languages to analyze