Add broccoli-conditional-debug and begin instrumenting.

[rwjblue]

Adds broccoli-conditional-debug as a dependency and begins instrumenting the styles portions of the build.

Once this lands, we can run a build like:

BROCCOLI_DEBUG=ember-engines:* ember b

And the instrumented trees are copied into ./DEBUG/ subfolder so that you can easily inspect them:

ember-engines:eager-in-eager:engine-style:input
ember-engines:eager-in-eager:styles
ember-engines:eager-in-lazy-in-lazy:engine-style:input
ember-engines:eager-in-lazy-in-lazy:styles
ember-engines:eager-in-lazy:engine-style:input
ember-engines:eager-in-lazy:styles
ember-engines:eager:engine-style:input
ember-engines:eager:styles
ember-engines:lazy-in-eager:engine-style:input
ember-engines:lazy-in-eager:engine-style:output
ember-engines:lazy-in-eager:engine-style:postprocessed
ember-engines:lazy-in-eager:styles
ember-engines:lazy-in-eager:vendor-style:input
ember-engines:lazy-in-eager:vendor-style:pre-import
ember-engines:lazy-in-lazy:engine-style:input
ember-engines:lazy-in-lazy:engine-style:output
ember-engines:lazy-in-lazy:engine-style:postprocessed
ember-engines:lazy-in-lazy:styles
ember-engines:lazy-in-lazy:vendor-style:input
ember-engines:lazy-in-lazy:vendor-style:pre-import
ember-engines:lazy:engine-style:input
ember-engines:lazy:engine-style:output
ember-engines:lazy:engine-style:postprocessed
ember-engines:lazy:styles
ember-engines:lazy:vendor-style:input
ember-engines:lazy:vendor-style:pre-import
ember-engines:tree-invocation-order:engine-style:input
ember-engines:tree-invocation-order:engine-style:output
ember-engines:tree-invocation-order:engine-style:postprocessed
ember-engines:tree-invocation-order:styles
ember-engines:tree-invocation-order:vendor-style:input
ember-engines:tree-invocation-order:vendor-style:pre-import

To only debug a single engine, you could run:

BROCCOLI_DEBUG=ember-engines:<engine name here>:* ember b

Which would output:

ember-engines:lazy-in-lazy:engine-style:input
ember-engines:lazy-in-lazy:engine-style:output
ember-engines:lazy-in-lazy:engine-style:postprocessed
ember-engines:lazy-in-lazy:styles
ember-engines:lazy-in-lazy:vendor-style:input
ember-engines:lazy-in-lazy:vendor-style:pre-import

[trentmwillis]

One smallish thing, but overall I like it!

[trentmwillis]

Minor suggestion: Can we create a helper function for constructing these labels? Maybe something like this._debugLabel('vendor-style:input'); and change the current _debugLabel to be _debugLabelPrefix or something?

It's not 100% necessary, but I feel it would be nicer and makes maintainability better in the long run (e.g. if we want to change the format or the labels).

[rwjblue]

Good point! I actually built something into broccoli-conditional-debug for this in https://github.com/rwjblue/broccoli-conditional-debug/pull/1.

[rwjblue]

@trentmwillis - Ready for another look when you have time...