fix: Ignore bump on new git repo without unreleased commits

[chme]

If a Git repository has no unreleased commits and only one version/tag, the original tag/version was ignored and instead the version was determined by the "bump" parameter.

For example:

gitGraph
    commit id: "A"
    commit id: "B" tag: "1.1.1"

Results in:

• with bump in (auto, major, minor, patch): Version "0.1.0"
• with bump a semver, e. g. "1.0.0": Version is the given semver, "1.0.0"

This PR fixes this by ignoring the bump parameter if there is only one tag and the tag is on the last commit.