QFile::permissions() returns old, cached value after call to QFile::setPermissions() on the same QFile object

Calling QFile::permissions() returns an out-of-date value after calling QFile::setPermissions() on the same object.

I can understand why QFile would not detect changes to the file's permissions outside of the QFile object, although if the permissions
change is done via QFile::setPermissions() then the object can clear its cached value automatically.

Test case:

#include <QtCore/QFile>

#include <QtDebug>

int main(int,char**)
{
    // create a file
    QFile file("test-file");
    file.open(QIODevice::WriteOnly);
    file.write(QByteArray("some data"));
    file.close();

    if (file.setPermissions(file.permissions() | QFile::WriteOther))
    {
        qDebug() << "new permissions (using old QFile object)" << (file.permissions() & QFile::WriteOther);
        qDebug() << "new permissions (using new QFile object)" << (QFile("test-file").permissions() & QFile::WriteOther);
    }

    file.remove();

    return 0;
}

Alternatively, the fact that permissions() returns a cached value should be documented.

A related issue is that there is no explicit refresh() method for QFile as there is for QFileInfo, although QFile::exists() does trigger a refresh when called.