Update index.js

[stefanpenner]

I believe we actually only want to recompute the cache if the favicon itself changes, without this we will rebuild for an input change. It may also be a good idea to have some sort of persistent cache, so initial boots aren't also so slow.

[davewasmer]

Ah didn't realize caching writer would use inputPaths to determine when the cache was busted.

As for the persistent cache, I'd love to, but broccoli-persistent-filter doesn't seem to support 1:N trees. See my comment on your issue.

[stefanpenner]

@davewasmer you should be able to add a persistent cache to anything even broccoli-caching-writer, ultimately persistent-filter just delegates to https://github.com/stefanpenner/async-disk-cache

[stefanpenner]

basically: build a cache key based on filePath + config + misc other stuff that might need to be around here: https://github.com/davewasmer/broccoli-favicon/blob/master/index.js#L59 then use https://github.com/stefanpenner/async-disk-cache.

The primitives aren't the best yet, but it should still be possible.