fix: allow changing media-type when pushing an image tag (#3022)

Fixes #3005

Previously, changing a image's media-type was disallowed.
However, "docker buildx" appears to first push an image manifest and
then an image index for the same image tag. So, allow this.

Signed-off-by: Ramkumar Chinchani <rchincha.dev@gmail.com>

pkg/api/controller_test.go

@@ -10835,13 +10835,13 @@ func TestManifestImageIndex(t *testing.T) {
 					resp, err = resty.R().SetHeader("Content-Type", ispec.MediaTypeImageIndex).
 						SetBody(content).Put(baseURL + "/v2/index/manifests/test:1.0")
 					So(err, ShouldBeNil)
-					So(resp.StatusCode(), ShouldEqual, http.StatusBadRequest)
+					So(resp.StatusCode(), ShouldEqual, http.StatusCreated)
 
 					// previously an image index, try writing a manifest
 					resp, err = resty.R().SetHeader("Content-Type", ispec.MediaTypeImageManifest).
 						SetBody(m1content).Put(baseURL + "/v2/index/manifests/test:index1")
 					So(err, ShouldBeNil)
-					So(resp.StatusCode(), ShouldEqual, http.StatusBadRequest)
+					So(resp.StatusCode(), ShouldEqual, http.StatusCreated)
 				})
 			})
 		})

pkg/storage/common/common.go

@@ -250,15 +250,9 @@ func CheckIfIndexNeedsUpdate(index *ispec.Index, desc *ispec.Descriptor,
 
 			// changing media-type is disallowed!
 			if manifest.MediaType != desc.MediaType {
-				err := zerr.ErrBadManifest
-				log.Error().Err(err).
+				log.Info().
 					Str("old mediaType", manifest.MediaType).
-					Str("new mediaType", desc.MediaType).Msg("cannot change media-type")
-
-				reason := fmt.Sprintf("changing manifest media-type from \"%s\" to \"%s\" is disallowed",
-					manifest.MediaType, desc.MediaType)
-
-				return false, "", zerr.NewError(err).AddDetail("reason", reason)
+					Str("new mediaType", desc.MediaType).Msg("media-type changed")
 			}
 
 			oldDesc := *desc

pkg/storage/s3/s3_test.go

@@ -3410,11 +3410,11 @@ func TestS3ManifestImageIndex(t *testing.T) {
 					So(digest, ShouldNotBeNil)
 
 					_, _, err = imgStore.PutImageManifest("index", "test:1.0", ispec.MediaTypeImageIndex, content)
-					So(err, ShouldNotBeNil)
+					So(err, ShouldBeNil)
 
 					// previously an image index, try writing a manifest
 					_, _, err = imgStore.PutImageManifest("index", "test:index1", ispec.MediaTypeImageManifest, m1content)
-					So(err, ShouldNotBeNil)
+					So(err, ShouldBeNil)
 				})
 			})
 		})