Add Global Grouping for Injections

[gabizou]

On discovering the @Group annotation, I've attempted to do something where I'd consider it a good feature for two redirects to be required to succeed only in an exclusive or situation (vanilla having a method, and forge rewriting that method or adding a new method signature, eliminating the vanilla form).

Somewhat similar to https://github.com/SpongePowered/Mixin/issues/297

Summary of discussion with Mumfrey about this:

Essentially, given two classes:

@Mixin(Foo.class) 
public class MixinFoo {

  @Group(name = "com.example.fully.qualified:groupname")
  @Redirect(method = "foo", at= @At(value = "INVOKE", target ="fqm()V")
  private void vanillaMethod() { }
}

@Mixin(Foo.class)
public class com.example.fully.qualified.mod.MixinFoo {

  @Group(name = "com.example.fully.qualified:groupname")
  @Redirect(method = "foo", at = @At(value = "INVOKE", target = "fqm(I)V")
  private void modifiedMethod(int var) { }
}

It would suffice to say that the following requirements would be set:

• @Group being applied on multiple injections would be "grouped" for the same target
• Evaluating min and max would be checked naturally at the end of injection validation
• Cross class grouping for the same targets should only work if the group has the same fully qualified name for the group (in this case com.example.fully.qualified:groupname). Non-qualified group names will only group injections in the same Mixin class.
• Qualifying group names is required to avoid cross contamination of other similarly named groups (if two groups have the name constructor, but come from different mods, we wouldn't want to contaminate either one)
• Avoids the intrinsic requirement of required from the global configuration between qualified projects, global groups can be configured through the root/parent providing mixing config.

Example of an existing setup with Group as this issue is intending: https://gist.github.com/gabizou/9a891cc8f68e1dc7506e9dce16571162

[Mumfrey]

Thanks for making this issue based on our discussion. I'm not going to add this to the 0.8 milestone but I'll start work on it immediately after.

[gabizou]

Just gonna comment to remind about the feature since 0.8 has been done, though there's other things that are likely being prioritized.

[Mumfrey]

Don't worry I haven't forgotten about it. I just haven't created a 0.9 milestone.