protected boolean quiet = false;
protected final void execute(Callback callback)
{
URL location = newResourceFactory(basedir).findResource(this.header);
Header header = readFrom(location, mergeProperties());
debug("Header %s:\n%s", header.getLocation(), header);
for(Document document : selectedDocuments())
{
if(document.isNotSupported())
{
warn("Unknown file extension: %s", document.getFile());