*LIBSMARTCOLS_DEBUG*=all::
enables libsmartcols debug output.

*LIBSMARTCOLS_DEBUG_PADDING*=on::
use visible padding characters.

*LIBSMARTCOLS_JSON*=compact|lines::
Controls JSON output format when using *--json*. Supported values are
*compact* for JSON output with minimal whitespace, and *lines* for JSON Lines
format (one JSON object per line). If unset or set to any other value,
pretty-printed JSON is used.
