Merge branch 'po/pretty-format-columns-doc'

Clarify column-padding operators in the pretty format string. * po/pretty-format-columns-doc: doc: pretty-formats note wide char limitations, and add tests doc: pretty-formats describe use of ellipsis in truncation doc: pretty-formats document negative column alignments doc: pretty-formats: delineate `%<|(` parameter values doc: pretty-formats: separate parameters from placeholders