[WORK] std.file.update function

[Stefan Koch via Digitalmars-d]

On Sunday, 18 September 2016 at 15:17:31 UTC, Andrei Alexandrescu 
wrote:
> There are quite a few situations in rdmd and dmd generally when 
> we compute a dependency structure over sets of files. Based on 
> that, we write new files that overwrite old, obsoleted files. 
> Those changes in turn trigger other dependencies to go stale so 
> more building is done etc.

If so we need it in druntime.

Introducing phobos into ddmd is still considered a nono.

Personally I am pretty torn, without range-specific optimizations 
in dmd they do incur more overhead then they should.