Looks like hashes is a hash now and blk can be nil.
Actually it looks like in the case of -b pointing to a buildpack on disk, this patch allows the upgrade to go without an exception, but the build still uses the default buildpacks rather than the one explicitly requested.
Not sure whether the latest commit on master was meant to address this, but I still need the second half of this patch to successfully build if there are any changes in my local working copy.
Hello. I apologize for not responding earlier but I am currently declaring Github bankruptcy. If this pull request or issue is still valid please feel free to re-open and explain.