Trying to run datasette (version 0.14) on Heroku with a metadata.json doesn't seem to be picking up the metadata.json file?

On a Mac with dodgy tar support:

 ▸    Couldn't detect GNU tar. Builds could fail due to decompression errors
 ▸    See
 ▸    https://devcenter.heroku.com/articles/platform-api-deploying-slugs#create-slug-archive
 ▸    Please install it, or specify the '--tar' option
 ▸    Falling back to node's built-in compressor

Could that be causing the issue?

Also, I'm not seeing custom query links anywhere obvious when I run the metadata file with a local datasette server?