Function: set-justification

Set the region's justification style to STYLE.
This commands prompts for the kind of justification to use.
If the mark is not active, this command operates on the current paragraph.
If the mark is active, it operates on the region. However, if the
beginning and end of the region are not at paragraph breaks, they are
moved to the beginning and end (respectively) of the paragraphs they
are in.

If variable `use-hard-newlines' is true, all hard newlines are
taken to be paragraph breaks.

When calling from a program, operates just on region between BEGIN and END,
unless optional fourth arg WHOLE-PAR is non-nil. In that case bounds are
extended to include entire paragraphs as in the interactive command.