Shell --export-page=all only exports first page

Convert a multipage PDF to SVG with this command:

inkscape multipage.pdf --pages=all --export-page=all --export-type=svg -o output.svg

Only the first page gets exported.

All pages should be exported.

Bug is in these 2 lines:

auto pages = Inkscape::parseIntRange(export_page);

Fix should be simple to make the magic value "all" work:

auto pages = Inkscape::parseIntRange(export_page, 1, __TOTAL_NUMBER_OF_PAGES_IN_DOC__);

Feature was introduced by @doctormo in !4691 (merged)