From https://parsoid-vs-core.wmflabs.org/diff/gomwiki/Template:%28%2Fdoc
$ echo "<table><td>[[</td><td>[[link]]</td><td>]]</td></table>" | php maintenance/run parse <table><tbody><tr><td>[[</td><td><a href="/index.php?title=Link&action=edit&redlink=1" class="new" title="Link (page does not exist)">link</a></td><td>]]</td></tr></tbody></table>
vs
$ echo "<table><td>[[</td><td>[[link]]</td><td>]]</td></table>" | php bin/parse.php <table data-parsoid='{"stx":"html","dsr":[0,54,7,8]}'><tbody data-parsoid='{"dsr":[7,46,0,0]}'><tr data-parsoid='{"autoInsertedStart":true,"dsr":[7,46,0,0]}'><td data-parsoid='{"stx":"html","dsr":[7,35,4,5]}'>[[</td><td><a rel="mw:WikiLink" href="./Link" title="Link" class="mw-disambig" data-parsoid='{"stx":"simple","a":{"href":"./Link"},"sa":{"href":"link"},"dsr":[22,30,2,2]}'>link</a></td><td data-parsoid='{"stx":"html","dsr":[35,46,4,5]}'>]]</td></tr></tbody></table>