Copying an std.stdio.File into another one

[0xEAB via Digitalmars-d-learn]

What's the correct way to copy a `File` into another one in D?
If `LockingTextReader` wasn't undocumented, I'd have gone for 
that approach:

import std.algorithm.mutation : copy;
import std.stdio : File, LockingTextReader;

void main()
{
    auto a = File("a.txt", "r");
    auto b = File("b.txt", "w");

    a.LockingTextReader.copy(b.lockingTextWriter);
}


Side-note:
Although the example code suggest otherwise, I'm not talking 
about copying actual files on disk. In such a case I'd just use 
`std.file.copy` ;)
So, just imagine `a` were `stdout` of process pipe.


Kind regards,
Elias