Feature Request: Option to use a release tag other than 'latest'

[joshmarinacci]

Circup is broken today because there is a bad release, and circup both requires a download first, and only downloads the latest release from GitHub. There are good reasons to require a download first, and a broken build is rare, but it would be useful to specify a git tag other than the latest release. I think this could be done by passing a tag option to the bundle download function. This tag would default to latest but could be overridden from the command line.

[Neradoc]

That would be useful, note however that there are multiple bundles (at least the Adafruit and community bundle), and they only get releases when there's a new library or a new release in one of the libraries, so there is no guarantee that a tag exists in both at the same time. This means that it would either need to default to latest or maybe use the tag as a cut-off date and get the most recent before that date, but that might be quite difficult, especially since we purposefully don't use the (potentially rate limited) github API in circup (also tags are not technically required to be dates). Realistically, if one wants a certain tag in the Adafruit bundle, it's probably fine to default to latest on others.