feat: Add zstd support

hcloudimages/client.go

@@ -104,9 +104,10 @@ const (
 	CompressionNone Compression = ""
 	CompressionBZ2  Compression = "bz2"
 	CompressionXZ   Compression = "xz"
+	CompressionZSTD Compression = "zstd"
 
 	// Possible future additions:
-	// zip,zstd
+	// zip
 )
 
 type Format string
@@ -524,6 +525,8 @@ func assembleCommand(options UploadOptions) (string, error) {
 			cmd += "bzip2 -cd | "
 		case CompressionXZ:
 			cmd += "xz -cd | "
+		case CompressionZSTD:
+			cmd += "zstd -cd | "
 		default:
 			return "", fmt.Errorf("unknown compression: %q", options.ImageCompression)
 		}

hcloudimages/client_test.go

@@ -48,6 +48,21 @@ func TestAssembleCommand(t *testing.T) {
 			},
 			want: "bash -c 'set -euo pipefail && wget --no-verbose -O - \"https://example.com/image.xz\" | xz -cd | dd of=/dev/sda bs=4M && sync'",
 		},
+		{
+			name: "local zstd",
+			options: UploadOptions{
+				ImageCompression: CompressionZSTD,
+			},
+			want: "bash -c 'set -euo pipefail && zstd -cd | dd of=/dev/sda bs=4M && sync'",
+		},
+		{
+			name: "remote zstd",
+			options: UploadOptions{
+				ImageURL:         mustParseURL("https://example.com/image.zst"),
+				ImageCompression: CompressionZSTD,
+			},
+			want: "bash -c 'set -euo pipefail && wget --no-verbose -O - \"https://example.com/image.zst\" | zstd -cd | dd of=/dev/sda bs=4M && sync'",
+		},
 		{
 			name: "local bz2",
 			options: UploadOptions{