diffpkg: allow to set column width for side-by-side view

The magic values `columns` and `auto` allow to set specific aspects,
with 'auto' as the default value:

- auto: Set width to the maximum line length of all input files
- columns: Set width to the shell defined $COLUMNS env var

Furthermore any number can be passed to set a static width.

0 files changed, 0 insertions, 0 deletions