Introduce a client interface, to abstract from buildkit client.

This will allow further enhancement like caching remote driver responses.

Signed-off-by: Silvin Lubecki <silvin.lubecki@docker.com>

driver/client.go

@@ -0,0 +1,20 @@
+package driver
+
+import (
+	"context"
+
+	controlapi "github.com/moby/buildkit/api/services/control"
+	"github.com/moby/buildkit/client"
+	gateway "github.com/moby/buildkit/frontend/gateway/client"
+)
+
+type Client interface {
+	Build(ctx context.Context, opt client.SolveOpt, product string, buildFunc gateway.BuildFunc, statusChan chan *client.SolveStatus) (*client.SolveResponse, error)
+	ListWorkers(ctx context.Context, opts ...client.ListWorkersOption) ([]*client.WorkerInfo, error)
+	Info(ctx context.Context) (*client.Info, error)
+	DiskUsage(ctx context.Context, opts ...client.DiskUsageOption) ([]*client.UsageInfo, error)
+	Prune(ctx context.Context, ch chan client.UsageInfo, opts ...client.PruneOption) error
+	ControlClient() controlapi.ControlClient
+	Close() error
+	Wait(ctx context.Context) error
+}