v2.12.0

Changed:

• Refactoring of ocrd_utils.__init__ into thematic submodules, #536
• validation of file groups downgraded to notice, allow PRE fileGrp/USE prefix, #541
• BaseProcessor: 🔥 show help if no METS was specified, OCR-D/spec#156, #438, #503

Fixed:

• bashlib: Don't set -x in ocrd__minversion, #535
• bashlib: ocrd__minversion logic was broken