Man page proposes --text-align=fill is a valid option, whereas it behaves exactly as default --text-align=left (see src/option.c:set_text_align() ). Besides that, the value of options.data.text_align is used for gtk_label_set_xalign(), which allows gdouble argument only (ie. "fill" is irrelevant in this context).
The gdouble value of options.data.text_align is also used for gtk_label_set_justify(), whereas it needs a proper enum here.
The proposed patch:
drops "fill" for --text-align;
makes --justify a global option (since both dialog text and text info affected);
properly use the combination of these options in the code.
Add .patch to filename :)