fs: Debug the names of env vars we read values from as part of the config

See: https://forum.rclone.org/t/how-can-i-check-if-environment-variables-are-being-used/17490

fs/config/config.go

@@ -172,7 +172,7 @@ func makeConfigPath() string {
 	// Check to see if user supplied a --config variable or environment
 	// variable.  We can't use pflag for this because it isn't initialised
 	// yet so we search the command line manually.
-	_, configSupplied := os.LookupEnv("RCLONE_CONFIG")
+	_, configSupplied := fs.LookupEnv("RCLONE_CONFIG")
 	if !configSupplied {
 		for _, item := range os.Args {
 			if item == "--config" || strings.HasPrefix(item, "--config=") {
@@ -311,7 +311,7 @@ func loadConfigFile() (*goconfig.ConfigFile, error) {
 		} else {
 			usingPasswordCommand = false
 
-			envpw := os.Getenv("RCLONE_CONFIG_PASS")
+			envpw := fs.Getenv("RCLONE_CONFIG_PASS")
 
 			if envpw != "" {
 				err := setConfigPassword(envpw)
@@ -1432,7 +1432,7 @@ func FileGetFlag(section, key string) (string, bool) {
 // It looks up defaults in the environment if they are present
 func FileGet(section, key string, defaultVal ...string) string {
 	envKey := fs.ConfigToEnv(section, key)
-	newValue, found := os.LookupEnv(envKey)
+	newValue, found := fs.LookupEnv(envKey)
 	if found {
 		defaultVal = []string{newValue}
 	}

fs/config/flags/flags.go

@@ -4,7 +4,6 @@ package flags
 
 import (
 	"log"
-	"os"
 	"time"
 
 	"github.com/rclone/rclone/fs"
@@ -15,7 +14,7 @@ import (
 // sets the default from the environment if possible.
 func setDefaultFromEnv(flags *pflag.FlagSet, name string) {
 	key := fs.OptionToEnv(name)
-	newValue, found := os.LookupEnv(key)
+	newValue, found := fs.LookupEnv(key)
 	if found {
 		flag := flags.Lookup(name)
 		if flag == nil {

fs/fs.go

@@ -1193,9 +1193,25 @@ func ParseRemote(path string) (fsInfo *RegInfo, configName, fsPath string, err e
 // A configmap.Getter to read from the environment RCLONE_CONFIG_backend_option_name
 type configEnvVars string
 
+// LookupEnv calls os.LookupEnv and Debugfs a message if the env var was found
+func LookupEnv(key string) (value string, ok bool) {
+	value, ok = os.LookupEnv(key)
+	if ok {
+		Debugf(nil, "Read env var %s", key)
+	}
+	return value, ok
+}
+
+// Getenv calls os.LookupEnv and Debugfs a message if the env var was
+// found. If the var wasn't round it returns empty string.
+func Getenv(key string) (value string) {
+	value, _ = LookupEnv(key)
+	return value
+}
+
 // Get a config item from the environment variables if possible
 func (configName configEnvVars) Get(key string) (value string, ok bool) {
-	return os.LookupEnv(ConfigToEnv(string(configName), key))
+	return LookupEnv(ConfigToEnv(string(configName), key))
 }
 
 // A configmap.Getter to read from the environment RCLONE_option_name
@@ -1211,12 +1227,12 @@ func (oev optionEnvVars) Get(key string) (value string, ok bool) {
 	}
 	// For options with NoPrefix set, check without prefix too
 	if opt.NoPrefix {
-		value, ok = os.LookupEnv(OptionToEnv(key))
+		value, ok = LookupEnv(OptionToEnv(key))
 		if ok {
 			return value, ok
 		}
 	}
-	return os.LookupEnv(OptionToEnv(oev.fsInfo.Prefix + "-" + key))
+	return LookupEnv(OptionToEnv(oev.fsInfo.Prefix + "-" + key))
 }
 
 // A configmap.Getter to read either the default value or the set