git show mylabel --pretty=format:"%H" --quiet

tag mylabel
Tagger: user <user@x.com>

Some comment

446a52cb4aff90d0626b8232aba8c40235c16245

git show-ref -s mylabel

<rev>^{}, e.g. v0.99.8^{}
       A suffix ^ followed by an empty brace pair means the object could be a tag, and dereference the tag recursively until a non-tag object is found.

git log <tag or branch> -n 1 --pretty=%H