This needs further work:
Type-1 SMF are always
"One [Ardour] track per [MIDI] track"
Only type-0 SMF have the option
"One [Ardour] track per [MIDI] channel"
and
"One [Ardour] track per [MIDI] file"
This is ambiguous with multi-channel audio or multiple selection,
mixed audio+midi and worse with mixed type0/1 .mid selection.
This calls for a dedicated dropdown to select MIDI Import Disposition
for type-0 SMF.
2a27cc4758