Add subcommand prune to the container, volume, image and system commands

Signed-off-by: Kenfe-Mickael Laventure <mickael.laventure@gmail.com>

client/image_prune.go

@@ -0,0 +1,26 @@
+package client
+
+import (
+	"encoding/json"
+	"fmt"
+
+	"github.com/docker/docker/api/types"
+	"golang.org/x/net/context"
+)
+
+// ImagesPrune requests the daemon to delete unused data
+func (cli *Client) ImagesPrune(ctx context.Context, cfg types.ImagesPruneConfig) (types.ImagesPruneReport, error) {
+	var report types.ImagesPruneReport
+
+	serverResp, err := cli.post(ctx, "/images/prune", nil, cfg, nil)
+	if err != nil {
+		return report, err
+	}
+	defer ensureReaderClosed(serverResp)
+
+	if err := json.NewDecoder(serverResp.body).Decode(&report); err != nil {
+		return report, fmt.Errorf("Error retrieving disk usage: %v", err)
+	}
+
+	return report, nil
+}