More Flexible App Selection in argocd-update Step

[wmiller112]

Checklist

• I've searched the issue queue to verify this is not a duplicate feature request.
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Proposed Feature

It would be nice to be able to select applications to be managed by a stage with argocd-update step by more than just a complete name.

Motivation

We've found as we add and remove applications, whether that be from adding/removing services or adding/removing clusters that existing services then get deployed to (by way of new applications generated by applicationsets), that we need to have some custom way of generating the list of apps a stage should be responsible for. I've handled this using argocd lovely plugin with a preprocessor that basically performs the functions of the argocd applicationset git file generator to create a kustomize patch with all the app names. This is fairly cumbersome and seems like it shouldn't be necessary at least from a security perspective, if we're already granting a particular stage permission to sync the application via the required kargo.akuity.io/authorized-stage annotation on the app side.

Suggested Implementation

Ability to select applications for sync by label or regex of the name.