Add information about manifest content types to API spec

Bring the spec up to date for schema2 changes.

Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>

docs/spec/api.md

@@ -125,6 +125,13 @@ reference and shouldn't be used outside the specification other than to
 identify a set of modifications.
 
 <dl>
+  <dt>k</dt>
+  <dd>
+    <ul>
+      <li>Document use of Accept and Content-Type headers in manifests endpoint.</li>
+    </ul>
+  </dd>
+
   <dt>j</dt>
   <dd>
     <ul>
@@ -408,6 +415,11 @@ GET /v2/<name>/manifests/<reference>
 The `name` and `reference` parameter identify the image and are required. The
 reference may include a tag or digest.
 
+The client should include an Accept header indicating which manifest content
+types it supports. For more details on the manifest formats and their content
+types, see manifest-v2-1.md and manifest-v2-2.md. In a successful response,
+the Content-Type header will indicate which manifest type is being returned.
+
 A `404 Not Found` response will be returned if the image is unknown to the
 registry. If the image exists and the response is successful, the image
 manifest will be returned, with the following format (see docker/docker#8093
@@ -822,6 +834,7 @@ Once all of the layers for an image are uploaded, the client can upload the
 image manifest. An image can be pushed using the following request format:
 
     PUT /v2/<name>/manifests/<reference>
+    Content-Type: <manifest media type>
 
     {
        "name": <name>,
@@ -839,7 +852,9 @@ image manifest. An image can be pushed using the following request format:
     }
 
 The `name` and `reference` fields of the response body must match those specified in
-the URL. The `reference` field may be a "tag" or a "digest".
+the URL. The `reference` field may be a "tag" or a "digest". The content type
+should match the type of the manifest being uploaded, as specified in
+manifest-v2-1.md and manifest-v2-2.md.
 
 If there is a problem with pushing the manifest, a relevant 4xx response will
 be returned with a JSON error message. Please see the _PUT Manifest section
@@ -1605,7 +1620,7 @@ The following parameters should be specified on the request:
 ```
 200 OK
 Docker-Content-Digest: <digest>
-Content-Type: application/json; charset=utf-8
+Content-Type: <media type of manifest>
 
 {
    "name": <name>,
@@ -1788,7 +1803,7 @@ Put the manifest identified by `name` and `reference` where `reference` can be a
 PUT /v2/<name>/manifests/<reference>
 Host: <registry host>
 Authorization: <scheme> <token>
-Content-Type: application/json; charset=utf-8
+Content-Type: <media type of manifest>
 
 {
    "name": <name>,

docs/spec/api.md.tmpl

@@ -125,6 +125,13 @@ reference and shouldn't be used outside the specification other than to
 identify a set of modifications.
 
 <dl>
+  <dt>k</dt>
+  <dd>
+    <ul>
+      <li>Document use of Accept and Content-Type headers in manifests endpoint.</li>
+    </ul>
+  </dd>
+
   <dt>j</dt>
   <dd>
     <ul>
@@ -408,6 +415,11 @@ GET /v2/<name>/manifests/<reference>
 The `name` and `reference` parameter identify the image and are required. The
 reference may include a tag or digest.
 
+The client should include an Accept header indicating which manifest content
+types it supports. For more details on the manifest formats and their content
+types, see manifest-v2-1.md and manifest-v2-2.md. In a successful response,
+the Content-Type header will indicate which manifest type is being returned.
+
 A `404 Not Found` response will be returned if the image is unknown to the
 registry. If the image exists and the response is successful, the image
 manifest will be returned, with the following format (see docker/docker#8093
@@ -822,6 +834,7 @@ Once all of the layers for an image are uploaded, the client can upload the
 image manifest. An image can be pushed using the following request format:
 
     PUT /v2/<name>/manifests/<reference>
+    Content-Type: <manifest media type>
 
     {
        "name": <name>,
@@ -839,7 +852,9 @@ image manifest. An image can be pushed using the following request format:
     }
 
 The `name` and `reference` fields of the response body must match those specified in
-the URL. The `reference` field may be a "tag" or a "digest".
+the URL. The `reference` field may be a "tag" or a "digest". The content type
+should match the type of the manifest being uploaded, as specified in
+manifest-v2-1.md and manifest-v2-2.md.
 
 If there is a problem with pushing the manifest, a relevant 4xx response will
 be returned with a JSON error message. Please see the _PUT Manifest section

registry/api/v2/descriptors.go

@@ -514,7 +514,7 @@ var routeDescriptors = []RouteDescriptor{
 									digestHeader,
 								},
 								Body: BodyDescriptor{
-									ContentType: "application/json; charset=utf-8",
+									ContentType: "<media type of manifest>",
 									Format:      manifestBody,
 								},
 							},
@@ -553,7 +553,7 @@ var routeDescriptors = []RouteDescriptor{
 							referenceParameterDescriptor,
 						},
 						Body: BodyDescriptor{
-							ContentType: "application/json; charset=utf-8",
+							ContentType: "<media type of manifest>",
 							Format:      manifestBody,
 						},
 						Successes: []ResponseDescriptor{