1. Use a Tag in the Branch Specifier.
2. Polling on the remote repo will occur.
3. It will run git ls-remote -h MY_REMOTE MY_TAG
4. This will result in nothing returned from the remote repository.

git ls-remote has a --tags option which will return the SHA of the Tag.

Polling is enabled because the Job also checkouts an SVN repository using the Jenkins Multiple SCMs plugin which doesn't refer to a tag.