never pull the docker container if pandoc is present and working in the PATH

internal/cli/app.go

@@ -106,12 +106,18 @@ func pandocMustExist(c *cli.Context) error {
 
 	pandocExistErr := pandocBinaryMustExist(c)
 	dockerExistErr := dockerMustExist(c)
+
 	config.SetPandoc(pandocExistErr == nil, dockerExistErr == nil)
 
 	if pandocExistErr != nil && dockerExistErr != nil {
 		return eitherMustExistErr
 	}
 
+	// if we don't have pandoc, but we do have docker, execute a pull
+	if pandocExistErr != nil && dockerExistErr == nil {
+		dockerPull(c)
+	}
+
 	return nil
 }
 
@@ -170,6 +176,23 @@ func dockerMustExist(c *cli.Context) error {
 		return dockerErr
 	}
 
+	_, err = cli.Ping(ctx)
+	if err != nil {
+		return dockerErr
+	}
+
+	return nil
+}
+
+func dockerPull(c *cli.Context) error {
+	dockerErr := fmt.Errorf("Docker must be available in order to run `%s`", c.Command.Name)
+
+	ctx := context.Background()
+	cli, err := client.NewEnvClient()
+	if err != nil {
+		return dockerErr
+	}
+
 	done := make(chan struct{})
 	defer close(done)