About 5 or more years ago we had a spate of unreliable/slow Monticello
repositories and the solution back then was to specify more than one
repository for packages/projects ... Metacello will cycle through the
list of repositories if there are failures/timeouts involved ... but
this means that you have to create a mirror repository ... and I would
think that if you are going to mirror a SmalltalkHub repository, your
best bet would be to mirror it as a filetree repo on github and then use
your locally cloned version of the repo and then you will never have
that problem again ...
You can create a local Monticello cache repository and then use
`repositoryOverrides:` in your Metacello load expression, but this isn't
an either/or propoosition ... when you use `repositoryOverrides:` you
really need to cache all of the mcz files locally ... this would
include mcz files for dependent projects (if any) ...
Again, if you are going to go about caching or mirroring, I think that
your best bet (these days) is to use github to mirror the entire repo ...