cli/command: add Cli.CurrentVersion() function

This internalizes constructing the Client(), which allows us to provide
fallbacks when trying to determin the current API version.

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

cli/command/cli.go

@@ -55,6 +55,7 @@ type Cli interface {
 	ServerInfo() ServerInfo
 	NotaryClient(imgRefAndAuth trust.ImageRefAndAuth, actions []string) (notaryclient.Repository, error)
 	DefaultVersion() string
+	CurrentVersion() string
 	ManifestStore() manifeststore.Store
 	RegistryClient(bool) registryclient.RegistryClient
 	ContentTrustEnabled() bool
@@ -86,6 +87,15 @@ func (cli *DockerCli) DefaultVersion() string {
 	return api.DefaultVersion
 }
 
+// CurrentVersion returns the API version currently negotiated, or the default
+// version otherwise.
+func (cli *DockerCli) CurrentVersion() string {
+	if cli.client == nil {
+		return api.DefaultVersion
+	}
+	return cli.client.ClientVersion()
+}
+
 // Client returns the APIClient
 func (cli *DockerCli) Client() client.APIClient {
 	return cli.client

cli/command/container/run.go

@@ -111,7 +111,7 @@ func runRun(dockerCli command.Cli, flags *pflag.FlagSet, ropts *runOptions, copt
 		reportError(dockerCli.Err(), "run", err.Error(), true)
 		return cli.StatusError{StatusCode: 125}
 	}
-	if err = validateAPIVersion(containerConfig, dockerCli.Client().ClientVersion()); err != nil {
+	if err = validateAPIVersion(containerConfig, dockerCli.CurrentVersion()); err != nil {
 		reportError(dockerCli.Err(), "run", err.Error(), true)
 		return cli.StatusError{StatusCode: 125}
 	}

cli/command/system/version.go

@@ -136,7 +136,7 @@ func runVersion(dockerCli command.Cli, opts *versionOptions) error {
 		Client: clientVersion{
 			Platform:          struct{ Name string }{version.PlatformName},
 			Version:           version.Version,
-			APIVersion:        dockerCli.Client().ClientVersion(),
+			APIVersion:        dockerCli.CurrentVersion(),
 			DefaultAPIVersion: dockerCli.DefaultVersion(),
 			GoVersion:         runtime.Version(),
 			GitCommit:         version.GitCommit,