Test failure seems unrelated.

I'm missing a line to actually pass the config value, will add soon.

Fixed, but still require ipfs/go-ipfs-config#41 to build.

@Stebalien what about this one ?

Unfortunately, I'm not sure how to add this in a backwards compatible manner (yet). If we add this as-is, the ARC cache will be disabled on all existing nodes as ARCCacheSize will default to 0.

We can ship a migration but I'd hate to do that. I believe the best way to do this is #8776.

Make sense to me.

Revisiting this, we can make progress on this without rewriting the config system. We now have types like config.Flag where we can encode both some type (e.g., a size as a string) or the "default" (null).

Basically, we'd need a new special "size" type with a default option.