api/image/list: Return Containers count

This parameter was already supported for some time in the backend (for
purposes related to docker system prune). It was also already present in
the imagetypes.ListOptions but was never actually handled by the client.

Make it available by default in the response.

Signed-off-by: Paweł Gronowski <pawel.gronowski@docker.com>

api/server/router/image/image_routes.go

@@ -459,6 +459,7 @@ func (ir *imageRouter) getImagesJSON(ctx context.Context, w http.ResponseWriter,
 	useNone := versions.LessThan(version, "1.43")
 	withVirtualSize := versions.LessThan(version, "1.44")
 	noDescriptor := versions.LessThan(version, "1.48")
+	noContainers := versions.LessThan(version, "1.51")
 	for _, img := range images {
 		if useNone {
 			if len(img.RepoTags) == 0 && len(img.RepoDigests) == 0 {
@@ -479,6 +480,9 @@ func (ir *imageRouter) getImagesJSON(ctx context.Context, w http.ResponseWriter,
 		if noDescriptor {
 			img.Descriptor = nil
 		}
+		if noContainers {
+			img.Containers = -1
+		}
 	}
 
 	return httputils.WriteJSON(w, http.StatusOK, images)

api/swagger.yaml

@@ -2196,8 +2196,7 @@ definitions:
           Number of containers using this image. Includes both stopped and running
           containers.
 
-          This size is not calculated by default, and depends on which API endpoint
-          is used. `-1` indicates that the value has not been set / calculated.
+          `-1` indicates that the value has not been set / calculated.
         x-nullable: false
         type: "integer"
         example: 2

api/types/image/opts.go

@@ -75,6 +75,8 @@ type ListOptions struct {
 	SharedSize bool
 
 	// ContainerCount indicates whether container count should be computed.
+	//
+	// Deprecated: This field has been unused and is no longer required and will be removed in a future version.
 	ContainerCount bool
 
 	// Manifests indicates whether the image manifests should be returned.