Function apply_prerelease 

pub fn apply_prerelease(
    current: &Version,
    level: BumpLevel,
    tag: &str,
) -> Version

Apply a pre-release bump. If the current version already has a pre-release tag matching tag, the numeric suffix is incremented. Otherwise, .0 is appended to the bumped version.

Example: 1.0.0 + Minor + tag "rc" → 1.1.0-rc.0 Example: 1.1.0-rc.0 + tag "rc" → 1.1.0-rc.1