eference updates the <code>&lt;old_value&gt;</code> and <code>&lt;new-value&gt;</code>
fields could denote references instead of objects. A reference will be
denoted with a <em>ref:</em> prefix, like <code>ref:&lt;ref-target&gt;</code>.</p>
</div>
<div class="paragraph">
<p>The exit status of the hook is ignored for any state except for the
"prepared" state. In the "prepared" state, a non-zero exit status will
cause the transaction to be aborted. The hook will not be called with
"aborted" state in that case