fs: factor OptionToEnv and ConfigToEnv into fs

fs/config.go

@@ -2,6 +2,7 @@ package fs
 
 import (
 	"net"
+	"strings"
 	"time"
 )
 
@@ -103,3 +104,16 @@ func NewConfig() *ConfigInfo {
 
 	return c
 }
+
+// ConfigToEnv converts an config section and name, eg ("myremote",
+// "ignore-size") into an environment name
+// "RCLONE_CONFIG_MYREMOTE_IGNORE_SIZE"
+func ConfigToEnv(section, name string) string {
+	return "RCLONE_CONFIG_" + strings.ToUpper(strings.Replace(section+"_"+name, "-", "_", -1))
+}
+
+// OptionToEnv converts an option name, eg "ignore-size" into an
+// environment name "RCLONE_IGNORE_SIZE"
+func OptionToEnv(name string) string {
+	return "RCLONE_" + strings.ToUpper(strings.Replace(name, "-", "_", -1))
+}