adding configs (arduino#65) not over

common/net_functions.go

@@ -107,7 +107,8 @@ func DownloadPackage(URL string, initialData *os.File, totalSize int64, handleRe
 
 	response, err := client.Do(request)
 	if err != nil {
-		return fmt.Errorf("Cannot fetch %s Response creation error: %s", URL, err)
+		return fmt.Errorf("Cannot fetch %s Response creation error: %s",
+			URL, err)
 	} else if response.StatusCode != 200 &&
 		response.StatusCode != 206 &&
 		response.StatusCode != 416 {

configs/configs.go

@@ -0,0 +1,85 @@
+/*
+ * This file is part of arduino-cli.
+ *
+ * arduino-cli is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ * As a special exception, you may use this file as part of a free software
+ * library without restriction.  Specifically, if other files instantiate
+ * templates or use macros or inline functions from this file, or you compile
+ * this file and link it with other files to produce an executable, this
+ * file does not by itself cause the resulting executable to be covered by
+ * the GNU General Public License.  This exception does not however
+ * invalidate any other reasons why the executable file might be covered by
+ * the GNU General Public License.
+ *
+ * Copyright 2017 BCMI LABS SA (http://www.arduino.cc/)
+ */
+
+package configs
+
+import (
+	"io/ioutil"
+	"os"
+
+	"gopkg.in/yaml.v2"
+)
+
+// Configs represents the possible configurations for the CLI.
+type Configs struct {
+	HTTPProxy      string `yaml:"HTTP_Proxy,omitempty"`
+	ConnectedBoard string `yaml:"ConnectedBoard,omitempty"`
+}
+
+// defaultConfig represents the default configuration.
+var defaultConfig = Configs{
+	HTTPProxy: os.Getenv("HTTP_PROXY"),
+}
+
+// Default returns a copy of the default configuration.
+func Default() Configs {
+	var def Configs
+	def = defaultConfig
+	return def
+}
+
+// Unserialize loads the configs from a yaml file.
+// Returns the default configuration if there is an
+// error.
+func Unserialize(path string) (Configs, error) {
+	content, err := ioutil.ReadFile(path)
+	if err != nil {
+		return Default(), err
+	}
+	var ret Configs
+	err = yaml.Unmarshal(content, &ret)
+	if err != nil {
+		return Default(), err
+	}
+	return ret, nil
+}
+
+// Serialize creates a file in the specified path with
+// corresponds to a config file reflecting the configs.
+func (c Configs) Serialize(path string) error {
+	content, err := yaml.Marshal(c)
+	if err != nil {
+		return err
+	}
+	err = ioutil.WriteFile(path, content, 0666)
+	if err != nil {
+		return err
+	}
+	return nil
+}