Use cases:

Adding post-update hooks, which requires diverting Ikiwiki's hook.

mv /srv/git/poop.git/hooks/post-update /srv/git/poop.git/hooks/post-update-ikiwiki
cat > /srv/git/poop.git/hooks/post-update
  #!/bin/sh
  /srv/git/poop.git/hooks/post-update-ikiwiki &
  echo This is a hook that does things!
cat > /srv/ikiwiki/piny/poop.setup.pl
  foreach(@{$conf->{wrappers}}) { $_->{wrapper} =~ s/post-update/post-update-ikiwiki/; };
rebuildrepo poop

Adding or removing plugins, or plugin confuration variables.

cat > /srv/ikiwiki/piny/poop.setup.pl
  push(@{$conf->{add_plugins}}, 'txt');
rebuildrepo poop

Any other special confuration requests from hosted projects.

cat > /srv/ikiwiki/piny/poop.setup.pl
  $conf->{teximg_prefix} .= "\n\\newcommand{\\unit}[1]{\\ensuremath{\\, \\mathrm{#1}}}"
rebuildrepo poop