 adapted for other replacements of build-in <code>TabExpansion2</code>.
It completes arguments of parameters <em>Task</em> (task names from a build file) and
<em>File</em> (normally suggests available <em>.build.ps1</em> and <em>.test.ps1</em> files).</p>
<p><strong>Warning on script output</strong></p>
<p>Output from scripts on adding tasks is treated as unexpected. It is intercepted
and written as a warning. Firstly, this catches a common mistake. Example: the
script outputs a script block instead of addi