Fix cache misses when pulling WSL machine image

Fixes a regression introduced by b2e6d53 that made always failing the
match of the WSL image from the registry with the image in the local
cache. The result was that the WSL machine image was always pulled from
quay.io even if an identical image was in the local cache.

Signed-off-by: Mario Loriedo <mario.loriedo@gmail.com>

pkg/machine/define/image_format.go

@@ -24,9 +24,6 @@ func (imf ImageFormat) Kind() string {
 }
 
 func (imf ImageFormat) KindWithCompression() string {
-	// Tar uses xz; all others use zstd
-	if imf == Tar {
-		return "tar.xz"
-	}
+	// All image formats are compressed with zstd
 	return fmt.Sprintf("%s.zst", imf.Kind())
 }

pkg/machine/define/image_format_test.go

@@ -59,9 +59,9 @@ func TestImageFormat_KindWithCompression(t *testing.T) {
 			imf:  Raw,
 			want: "raw.zst",
 		}, {
-			name: "tar.xz",
+			name: "tar.zst",
 			imf:  Tar,
-			want: "tar.xz",
+			want: "tar.zst",
 		},
 	}
 	for _, tt := range tests {