'Determine the component version from the \'version-X.Y.Z\' git tag.
Args:
comp [string]: Spinnaker component name.
Returns:
[string] Component version with build number and without \'version-\'.'

def __version_from_tag(self, comp):

    version_bump = dict((self.__component_versions.items() + self.__halyard_version.items()))[comp]
    next_tag_with_build = '{0}-{1}'.format(version_bump.version_str, self.build_number)
    first_dash_idx = next_tag_with_build.index('-')
    return next_tag_with_build[(first_dash_idx + 1):]
