The Mercurial historyurl in the example ikiwiki.setup file creates a link to the repo's summary page. It should take you to the history page for the file, like the example Git historyurl does.
The current historyurl is:
#historyurl => "http://localhost:8000/", # hg serve'd local repository
A link to the history page for the file would be:
#historyurl => "http://localhost:8000/log/tip/[[file]]", # hg serve'd local repository
The backslash in the code should be removed.
This creates links to the hgweb page which is equivalent to the Git file history page.