systemjs/systemjs — pull request #189 by guybedford (2014-08-23 00:55:16+00:00)
Title: Conditionals

This PR adds support for conditional configuration.

It runs through meta configuration, which makes the API really simple -

```javascript
System.meta['some/module'] = {
condition: './condition-module',
branches: {
value1: './module1',
value2: './module2'
}
};
```

This PR runs against the new package configuration (first commit here). So conditionals can also be set though package meta:

```javascript
System.packages['some/package'] = {
meta: {
'some/path': {
condition: './environment',
branches: {
'ie': './some/path-ie',
}
}
}
};
```

The other nice thing about using meta for conditionals is they can even be written naturally using meta-syntax within source files in due course (when we support `"branches.ie value"` style lookups in meta).