* Only use `git verify-tag` when verifying annotated tags
The command `git verify-tag` only applies to annotated tags. When
verifying lightweight tags, which are more similar to non-moving
branches, one has to use `git verify-commit` instead.
Using ':' as a separator is appropriate since that is one of the
characters not allowed in a Git reference name.
See also https://www.kernel.org/pub/software/scm/git/docs/git-check-ref-format.html
* Improve testing of the Git module's gpg verification
