Currently, users can only create ApplicationSets by applying configurations declaratively using kubectl. Introducing support for CLI/UI would improve the overall experience for managing large number of applications using ApplicationSet.

Proposal Doc: https://github.com/ishitasequeira/argo-cd/blob/master/docs/proposals/backend-support-appset.md

Acceptance Criteria:

• Users should be able to create/update/delete ApplicationSets using argocd CLI
• Add a new argocd command option appset with create, delete, update and list sub-commands.