cli/command: use shallower interface for completions

The completion functions only need the API-client, and not all of
the CLI. However, passing the API-client as argument would mean
that the API-client is initialized early, which may not be what
we want, so instead, defining an APIClientProvider interface to
preserve the behavior of initializing when needed only.

While updating, also simplify stack.format to only require an
io.Writer.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

cli/command/stack/swarm/list.go

@@ -3,16 +3,16 @@ package swarm
 import (
 	"context"
 
-	"github.com/docker/cli/cli/command"
 	"github.com/docker/cli/cli/command/stack/formatter"
 	"github.com/docker/cli/cli/compose/convert"
 	"github.com/docker/docker/api/types"
+	"github.com/docker/docker/client"
 	"github.com/pkg/errors"
 )
 
 // GetStacks lists the swarm stacks.
-func GetStacks(ctx context.Context, dockerCli command.Cli) ([]*formatter.Stack, error) {
-	services, err := dockerCli.Client().ServiceList(
+func GetStacks(ctx context.Context, apiClient client.ServiceAPIClient) ([]*formatter.Stack, error) {
+	services, err := apiClient.ServiceList(
 		ctx,
 		types.ServiceListOptions{Filters: getAllStacksFilter()})
 	if err != nil {