cacheDirectory deprecated in 0.13...so now what?

Question

Asked this on the sbt mailing list, but apparently it is being phased out

I created a project on github that works around "sbt> clean" from blowing away artifact update cache directory. Works great on 0.12.4, but broken in 0.13, my custom update cache directory is empty after "sbt> update"

What's the equivalent of:

cacheDirectory <<= baseDirectory / "sbt-no-clean"

in 0.13? I see that cacheDirectory has been deprecated and that we are to use streams instead.

The SBT FAQ for 0.13 has a section on using FileFunction.cached, is that the replacement for above 1 liner? Doesn't look like it.

Streams may indeed do the job, but since old method of working with cacheDirectory no longer works -- well, technically the attribute is set, but something overrides it, so it's more of a removal than deprecation functionality-wise -- I have shifted gears and am trying to use cleanKeepFiles:

cleanKeepFiles <<= (streams) map{s=> Seq(s.cacheDirectory)}

I get a return type mismatch, a maddening one at that, as I have no idea how to turn:

sbt.Def.Initialize[sbt.Task[Seq[java.io.File]]]

into

sbt.Def.Initialize[Seq[java.io.File]]

Ideas appreciated, Thanks

EDIT
If you use apply instead of map:

cleanKeepFiles <<= streams.apply{_.map(x=>Seq(x.cacheDirectory))}

then you get:

sbt.Task[Seq[java.io.File]]

which seems to be getting closer, but then the compiler wants:

Seq[java.io.File]

cleanKeepFiles is of type SettingKey[Seq[File]]

I am beyond confused as to how to get a SettingKey[Seq[File]] out of stream's type: TaskKey[TaskStreams]

Answer 1

Totally forgot about posting this question, solution was thankfully pretty simple:

cleanKeepFiles <+= base / pathToCacheDir

That prevents SBT from blowing away deps cache on every single clean, which shaves a few seconds off clean/compile cycles -- a nice & easy WIN, just like we were able to do with cacheDirectory in SBT <= 0.12.4