osbuild2: support VMDK subformat in the QEMU stage

Support setting a specific VMDK subformat in the type format options.

The required osbuild version in the SPEC file is not bumped, since the
new functionality is currently not used by any image type.

Related to https://github.com/osbuild/osbuild/pull/999

internal/osbuild2/qemu_stage.go

@@ -21,6 +21,7 @@ type QEMUStageOptions struct {
 func (QEMUStageOptions) isStageOptions() {}
 
 type QEMUFormat string
+type VMDKSubformat string
 
 const (
 	QEMUFormatQCOW2 QEMUFormat = "qcow2"
@@ -28,6 +29,12 @@ const (
 	QEMUFormatVMDK  QEMUFormat = "vmdk"
 	QEMUFormatVPC   QEMUFormat = "vpc"
 	QEMUFormatVHDX  QEMUFormat = "vhdx"
+
+	VMDKSubformatMonolithicSparse     VMDKSubformat = "monolithicSparse"
+	VMDKSubformatMonolithicFlat       VMDKSubformat = "monolithicFlat"
+	VMDKSubformatTwoGbMaxExtentSparse VMDKSubformat = "twoGbMaxExtentSparse"
+	VMDKSubformatTwoGbMaxExtentFlat   VMDKSubformat = "twoGbMaxExtentFlat"
+	VMDKSubformatStreamOptimized      VMDKSubformat = "streamOptimized"
 )
 
 type QEMUFormatOptions interface {
@@ -83,6 +90,8 @@ func (o VPCOptions) validate() error {
 type VMDKOptions struct {
 	// The type of the format must be 'vpc'
 	Type QEMUFormat `json:"type"`
+
+	Subformat VMDKSubformat `json:"subformat,omitempty"`
 }
 
 func (VMDKOptions) isQEMUFormatOptions() {}
@@ -91,6 +100,27 @@ func (o VMDKOptions) validate() error {
 	if o.Type != QEMUFormatVMDK {
 		return fmt.Errorf("invalid format type %q for %q options", o.Type, QEMUFormatVMDK)
 	}
+
+	if o.Subformat != "" {
+		allowedVMDKSubformats := []VMDKSubformat{
+			VMDKSubformatMonolithicFlat,
+			VMDKSubformatMonolithicSparse,
+			VMDKSubformatTwoGbMaxExtentFlat,
+			VMDKSubformatTwoGbMaxExtentSparse,
+			VMDKSubformatStreamOptimized,
+		}
+		valid := false
+		for _, value := range allowedVMDKSubformats {
+			if o.Subformat == value {
+				valid = true
+				break
+			}
+		}
+		if !valid {
+			return fmt.Errorf("'subformat' option does not allow %q as a value", o.Subformat)
+		}
+	}
+
 	return nil
 }