Vignette: How to supplement a metric repo

[dgkf]

As discussed in team meeting on 2025/08/21

Question came up asking how an org could mix in their own metrics. Since this might be a common fear of adoption open-source tooling, we should make it clear that we support extension and how that would be achieved.

Vignette should show:

• how to register a new metric (can link to val.meter vignette which discusses this at length)
• what it would look like to build a supplementary PACKAGES file containing the new metric
• how to use metrics coming from two separate metric repositories to filter on a mix of filter criteria

For the sake of example, maybe we could

1. Implement the "reputable_maintainer" metric - checking if R Validation Hub is the copyright holder
2. Simulate the metric for a demo "acme" org repo
3. Show how both metric repos can be joined and leverage our same tools to impose a filtering criteria

options(
  val.criterion.repos = c(
     "valor" = "https://pharmar.org/cran-metrics", 
     "acme" = "https://acme.org/metrics"
  ),
  available_packages_filters = package_filter({
    # is externally popular 
    percentile(valor$downloads_total) > 0.25 | 

    # has a really good maintainer
    acme$reputable_maintainer
  })
)