Added support for adding custom arguments to tools.

[patriksvensson]

Closes #500

[gep13]

@patriksvensson there seems to be something screwy going on here:

with the names of the files in this PR.

Any ideas?

[patriksvensson]

@gep13 It's just a convention to name files containing generic classes using the CRef naming (i.e. T:TestNamespace.GenericClass```1). We hadn't had the need for it before since there are no classes with the same name that only differs by generic argument count. CoreFX for example uses the same conventions.

Can change it to something else if you want to, but I think we should have some convention for it.

[gep13]

@patriksvensson Gotcha! No, no need to change it. I just hadn't seen this before. My initial thought was that something had gone wrong with a merge/rebase etc, and the file name had got mangled 😄 Makes sense now that you explain it. Good to know, thanks!

[devlead]

Wonder if it would make sense to have it be a Func instead if Action instead

public Func<ProcessArgumentBuilder, ProcessArgumentBuilder> ArgumentCustomization { get; set; }

so we could modify and return same instance, with the extension methods:

Settings.ArgumentCustomization = arg=>arg.Append("-true");

,but also just as easily return a new instance/exsisting instance.

Settings.ArgumentCustomization = arg=>"my new arguments";
...
Settings.ArgumentCustomization = arg=>reUseExistingArguments;
...
Settings.ArgumentCustomization = arg=>GetCustomNewArgs(param1, param2);

[patriksvensson]

We could add an extension method for this, but just providing an Action is probably simpler and fits the most common use case where you want to add an argument that is missing.

If you completely want to rewrite the arguments, you could simply use the builder.Clear() method before adding your arguments.

[devlead]

I kinda disagree, but might be personal preference.
Personally don't think this is unclean, unclear or less fluent.

Settings.ArgumentCustomization = builder=>"arg"

vs.

Settings.ArgumentCustomization = builder => {  
    builder.Clear();
    builder.Append("Arg");
};

As the all the extension methods return a ProcessArgumentBuilder it would just work without any code change.

I would just find a Func more flexible with little added complexity, would support any scenario the Action does plus a few more.

[patriksvensson]

I think this one is ready to be merged 👍