post-commit hook executed *only* if new tag committed?

Hello,

I've spent most of the afternoon searching the web for this, so my apologies
if the answer is obvious.

I'm hoping to implement a post-commit script that will update files on a
production website *only* if a new tag is assigned to my project in the
repository.

I want to be able to commit a variety of changes over time, and then only
when I tag the repository as ready for the next production version do I want
the production website updated.

Is this possible?

Thanks,

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Eric White