distro: add ListArchs() to Distro interface

Similar to ListImageTypes() add a helper to enumerate the supported
architectures.

Signed-off-by: Tom Gundersen <teg@jklm.no>

internal/distro/distro.go

@@ -24,6 +24,10 @@ type Distro interface {
 	// for modularity support.
 	ModulePlatformID() string
 
+	// Returns a sorted list of the names of the architectures this distro
+	// supports.
+	ListArchs() []string
+
 	// Returns an object representing the given architecture as support
 	// by this distro.
 	GetArch(arch string) (Arch, error)

internal/distro/fedora30/distro.go

@@ -56,6 +56,15 @@ type fedora30ImageType struct {
 	imageType *imageType
 }
 
+func (d *Fedora30) ListArchs() []string {
+	archs := make([]string, 0, len(d.arches))
+	for name := range d.arches {
+		archs = append(archs, name)
+	}
+	sort.Strings(archs)
+	return archs
+}
+
 func (d *Fedora30) GetArch(arch string) (distro.Arch, error) {
 	a, exists := d.arches[arch]
 	if !exists {

internal/distro/fedora31/distro.go

@@ -56,6 +56,15 @@ type fedora31ImageType struct {
 	imageType *imageType
 }
 
+func (d *Fedora31) ListArchs() []string {
+	archs := make([]string, 0, len(d.arches))
+	for name := range d.arches {
+		archs = append(archs, name)
+	}
+	sort.Strings(archs)
+	return archs
+}
+
 func (d *Fedora31) GetArch(arch string) (distro.Arch, error) {
 	a, exists := d.arches[arch]
 	if !exists {

internal/distro/fedora32/distro.go

@@ -56,6 +56,15 @@ type fedora32ImageType struct {
 	imageType *imageType
 }
 
+func (d *Fedora32) ListArchs() []string {
+	archs := make([]string, 0, len(d.arches))
+	for name := range d.arches {
+		archs = append(archs, name)
+	}
+	sort.Strings(archs)
+	return archs
+}
+
 func (d *Fedora32) GetArch(arch string) (distro.Arch, error) {
 	a, exists := d.arches[arch]
 	if !exists {

internal/distro/fedoratest/distro.go

@@ -24,6 +24,10 @@ type fedoraTestDistroImageType struct {
 	arch *fedoraTestDistroArch
 }
 
+func (d *FedoraTestDistro) ListArchs() []string {
+	return []string{"x86_64"}
+}
+
 func (d *FedoraTestDistro) GetArch(arch string) (distro.Arch, error) {
 	if arch != "x86_64" {
 		return nil, errors.New("invalid architecture: " + arch)

internal/distro/rhel81/distro.go

@@ -57,6 +57,15 @@ type rhel81ImageType struct {
 	imageType *imageType
 }
 
+func (d *RHEL81) ListArchs() []string {
+	archs := make([]string, 0, len(d.arches))
+	for name := range d.arches {
+		archs = append(archs, name)
+	}
+	sort.Strings(archs)
+	return archs
+}
+
 func (d *RHEL81) GetArch(arch string) (distro.Arch, error) {
 	a, exists := d.arches[arch]
 	if !exists {

internal/distro/rhel82/distro.go

@@ -57,6 +57,15 @@ type rhel82ImageType struct {
 	imageType *imageType
 }
 
+func (d *RHEL82) ListArchs() []string {
+	archs := make([]string, 0, len(d.arches))
+	for name := range d.arches {
+		archs = append(archs, name)
+	}
+	sort.Strings(archs)
+	return archs
+}
+
 func (d *RHEL82) GetArch(arch string) (distro.Arch, error) {
 	a, exists := d.arches[arch]
 	if !exists {

internal/distro/test/distro.go

@@ -16,6 +16,10 @@ type testImageType struct{}
 const name = "test-distro"
 const modulePlatformID = "platform:test"
 
+func (d *TestDistro) ListArchs() []string {
+	return []string{"test_arch"}
+}
+
 func (d *TestDistro) GetArch(arch string) (distro.Arch, error) {
 	if arch != "test_arch" {
 		return nil, errors.New("invalid arch: " + arch)