[chef] render partial template only if the node['fqdn']-partial exists

Hiya,

How can I render a base template *plus* a partial template only if the partial
exists for node['fqdn']? Is there a way to do this? The way I see it now, the
only way I can do this is to create a per-fqdn erb files in my cookbook for
every host, even if only a few of them actually need to render the partial. 
I'll
bet there's a better way to do this, I just don't see it yet.

Let's say I have a bunch of mysql database hosts, and most of them can render
their my.cnf following one standard. And let's say sometimes I have a need to
extend the standard by appending extra config lines for only some of the db
hosts.

Here are examples of the rendered my.cnf I want, the first is for a db host 
that
has no special config lines, the second for a db host that needs a lil extra:

  [mysqld]
  server-id = 14050101
  report-host = db14b.dev.example.com
  !include /etc/mysql/_my.cnf_m3.large
  !include /etc/mysql/_my.cnf.global_5.5


  [mysqld]
  server-id = 14050701
  report-host = db26b.dev.example.com
  !include /etc/mysql/_my.cnf_m3.large
  !include /etc/mysql/_my.cnf.global_5.5
  #
  # special stuff for this host is below, brought to you by chef partial 
template:
  [mysqld]
  expire_logs_days=5
  replicate-wild-ignore-table = foo_bar.KBToyAndHobby%


The template resource in the recipe:

  template "/etc/mysql/my.cnf" do
    source "my.cnf.erb"
    owner "root"
    group "root"
    mode 00644
    variables :server_id     => node['tokopf-bar']['mysql']['server_id'],
              :mysql_version => node['tokopf-bar']['mysql']['mysql_version']
  end


The main template, my.cnf.erb:
  [mysqld]
  server-id = <%= @server_id %>
  report-host = <%= node['fqdn'] %>
  !include /etc/mysql/_my.cnf_<%= node['ec2']['instance_type'] %>
  !include /etc/mysql/_my.cnf.global_<%= @mysql_version %>
  <%= render @node['fqdn'] + ".mycnf-partial.erb" -%>


cookbooks/tokopf-bar/templates/default/db14b.dev.example.com.mycnf-partial.erb
 is empty...

cookbooks/tokopf-bar/templates/default/db26b.dev.example.com.mycnf-partial.erb:
  #
  # special stuff for this host is below, brought to you by chef partial 
template:
  [mysqld]
  expire_logs_days=5
  replicate-wild-ignore-table = foo_bar.KBToyAndHobby%


Thanks!
kallen