Command line parsing

[Andrei Alexandrescu via Digitalmars-d]

I found this in https://peter.bourgon.org/go-best-practices-2016/:

"I said it in 2014 but I think it’s important enough to say again: 
define and parse your flags in func main. Only func main has the right 
to decide the flags that will be available to the user. If your library 
code wants to parameterize its behavior, those parameters should be part 
of type constructors. Moving configuration to package globals has the 
illusion of convenience, but it’s a false economy: doing so breaks code 
modularity, makes it more difficult for developers or future maintainers 
to understand dependency relationships, and makes writing independent, 
parallelizable tests much more difficult."

This is interesting because it's what std.getopt does but the opposite 
of what GFLAGS (http://gflags.github.io/gflags/) does. GFLAGS allows any 
module in a project to define flags. I was thinking of adding 
GFLAGS-like capabilities to std.getopt but looks like there's no need 
to... thoughts?


Andrei