TagBot always notify that a new tag is expected when registering subpackage

[ErikQQY]

The TagBot helps check if there exists a tag with JuliaTagBot, but in some big packages with sub-packages, when we cut a release for a sub-package and do nothing about the parent package, TagBot would warn this every 4 hours:

Triggering TagBot for merged registry pull request

This extra notification is being sent because I expected a tag to exist by now, but it doesn't.
You may want to check your TagBot configuration to ensure that it's running, and if it is, check the logs to make sure that there are no errors.

I think the Tagbot is trying to check if there are tags for the new released sub-package but instead it checked the parent package. Is it intended or a bug? For example, this issue exists in SciML/OrdinaryDiffEq.jl#1295 (comment) and SciML/NonlinearSolve.jl#14 (comment)

[ErikQQY]

Seems duplicate of #241