cli: pass dockerCLI's in/out/err to cobra cmds

Both the DockerCLI and Cobra Commands provide accessors for Input, Output,
and Error streams (usually STDIN, STDOUT, STDERR). While we were already
passing DockerCLI's Output to Cobra, we were not doing so for the other
streams (and were passing none for plugin commands), potentially resulting
in DockerCLI output/input to mean something else than a Cobra Command's
intput/output/error.

This patch sets them to the same streams when constructing the Cobra
command.

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

cli-plugins/plugin/plugin.go

@@ -133,7 +133,9 @@ func newPluginCommand(dockerCli *command.DockerCli, plugin *cobra.Command, meta
 	}
 	opts, flags := cli.SetupPluginRootCommand(cmd)
 
+	cmd.SetIn(dockerCli.In())
 	cmd.SetOut(dockerCli.Out())
+	cmd.SetErr(dockerCli.Err())
 
 	cmd.AddCommand(
 		plugin,

cmd/docker/docker.go

@@ -51,6 +51,10 @@ func newDockerCommand(dockerCli *command.DockerCli) *cli.TopLevelCommand {
 			DisableDescriptions: true,
 		},
 	}
+	cmd.SetIn(dockerCli.In())
+	cmd.SetOut(dockerCli.Out())
+	cmd.SetErr(dockerCli.Err())
+
 	opts, flags, helpCmd = cli.SetupRootCommand(cmd)
 	registerCompletionFuncForGlobalFlags(dockerCli, cmd)
 	flags.BoolP("version", "v", false, "Print version information and quit")