# if you use exclusively lightweigth tags :
git show-refs --tags | grep $(git rev-parse HEAD)
# also check that the tag looks like a build tag, e.g : refs/tags/1.2.3.4
   | grep "refs/tags/[1-9.]*$"

# if you use annotated tags :
git show-refs --tags --dereference | grep $(git rev-parse HEAD)
# the grepped line may look like : refs/tags/1.2.3.4^{}
   | grep -E "refs/tags/[1-9.]*(^{})?$"