If you force-push to a source repository that is the configured git repository for the ikiwiki srcdir, rebuilding the wiki (after the hook) fails with

fatal: refusing to merge unrelated histories
'git pull --prune origin' failed:  at /usr/local/share/perl/5.28.1/IkiWiki/Plugin/git.pm line 251.

I think that under some circumstances ikiwiki should support this. Perhaps via configuration options for the git plugin. — Jon