Use scratch space as the default option for most imports

Since we dropped the use of nbdkit we've started prioritizing the use of scratch space for most import flows.

However, this new behavior introduced minor differences such as stop converting raw images, which caused inconsistencies in some tests.

This commit improves the importer flow to better determine whether to use scratch space or not.

Signed-off-by: Alvaro Romero <alromero@redhat.com>

pkg/importer/format-readers.go

@@ -174,15 +174,15 @@ func (fr *FormatReaders) fileFormatSelector(hdr *image.Header) {
 			fr.Archived = true
 			fr.ArchiveZstd = true
 		}
-	case "qcow2":
-		r, err = fr.qcow2NopReader(hdr)
-		fr.Convert = true
 	case "xz":
 		r, err = fr.xzReader()
 		if err == nil {
 			fr.Archived = true
 			fr.ArchiveXz = true
 		}
+	case "qcow2":
+		r, err = fr.qcow2NopReader(hdr)
+		fr.Convert = true
 	case "vmdk":
 		r = nil
 		fr.Convert = true

pkg/importer/http-datasource.go

@@ -133,19 +133,13 @@ func (hs *HTTPDataSource) Info() (ProcessingPhase, error) {
 	if hs.contentType == cdiv1.DataVolumeArchive {
 		return ProcessingPhaseTransferDataDir, nil
 	}
-	if !hs.readers.Convert {
-		return ProcessingPhaseTransferDataFile, nil
-	}
 	if pullMethod, _ := util.ParseEnvVar(common.ImporterPullMethod, false); pullMethod == string(cdiv1.RegistryPullNode) {
 		hs.url, _ = url.Parse(fmt.Sprintf("nbd+unix:///?socket=%s", nbdkitSocket))
 		if err = hs.n.StartNbdkit(hs.endpoint.String()); err != nil {
 			return ProcessingPhaseError, err
 		}
 		return ProcessingPhaseConvert, nil
 	}
-	// removing check for hs.brokenForQemuImg, and always assuming it is true
-	// revert once we are able to get nbdkit 1.35.8, which contains a fix for the
-	// slow download speed.
 	return ProcessingPhaseTransferScratch, nil
 }