Sort unknown versions higher in bump sort

When using "bump" sort, place images for which version could not be
identified in between the group of outdated and updated images. This
improves the UX as their state is unknown, but similar to other images
of the same state.

internal/semver/utils.go

@@ -86,12 +86,17 @@ func LatestOpinionatedVersionString(current string, versions []string) (string,
 // used to diff two versions of the same image. The resulting diff is sortable
 // among with calculated values. Might fall apart if there are many parts, but
 // most of the time, there are only three or four version parts.
+// Note that it is valid to pass a nil [Version], which will be treated as a
+// unknown version.
 func PackInt64(version *Version) uint64 {
-	var packed uint64
+	if version == nil {
+		return 1
+	}
 
-	bitsPerPart := 64 / len(version.Release)
+	var packed uint64
+	bitsPerPart := 63 / len(version.Release)
 	for i, part := range version.Release {
-		packed |= uint64(part) << uint64((len(version.Release)-i-1)*bitsPerPart)
+		packed |= uint64(part) << uint64((len(version.Release)-i-1)*bitsPerPart+1)
 	}
 
 	return packed

internal/worker/worker.go

@@ -99,15 +99,17 @@ func (w *Worker) ProcessRawImage(ctx context.Context, reference oci.Reference) e
 		// Fallthrough - insert what we have
 	}
 
+	versionDiffSortable := semver.PackInt64(nil)
+
 	// If no new version was defined and the current version is using the "latest"
 	// convention, the latest available reference is the current reference
-	if reference.Version() == "latest" && data.LatestReference == nil {
+	if reference.Version() == "latest" {
 		r := reference
 		data.LatestReference = &r
+		versionDiffSortable = 0
 	}
 
 	// Add some basic tags
-	var versionDiffSortable uint64
 	if data.LatestReference != nil {
 		if data.ImageReference.String() == data.LatestReference.String() {
 			data.Tags = append(data.Tags, "up-to-date")