fs/config: Add method to reload configfile from disk

Fixes #3268

fs/config/config.go

@@ -1340,6 +1340,16 @@ func FileDeleteKey(section, key string) bool {
 
 var matchEnv = regexp.MustCompile(`^RCLONE_CONFIG_(.*?)_TYPE=.*$`)
 
+// FileRefresh ensures the latest configFile is loaded from disk
+func FileRefresh() error {
+	reloadedConfigFile, err := loadConfigFile()
+	if err != nil {
+		return err
+	}
+	configFile = reloadedConfigFile
+	return nil
+}
+
 // FileSections returns the sections in the config file
 // including any defined by environment variables.
 func FileSections() []string {

fs/config/config_test.go

@@ -1,6 +1,7 @@
 package config
 
 import (
+	"bytes"
 	"fmt"
 	"io/ioutil"
 	"os"
@@ -292,3 +293,21 @@ func TestMatchProvider(t *testing.T) {
 		assert.Equal(t, test.want, got, what)
 	}
 }
+
+func TestFileRefresh(t *testing.T) {
+	defer testConfigFile(t, "refresh.conf")()
+	require.NoError(t, CreateRemote("refresh_test", "config_test_remote", rc.Params{
+		"bool": true,
+	}))
+	b, err := ioutil.ReadFile(ConfigPath)
+	assert.NoError(t, err)
+
+	b = bytes.Replace(b, []byte("refresh_test"), []byte("refreshed_test"), 1)
+	err = ioutil.WriteFile(ConfigPath, b, 0644)
+	assert.NoError(t, err)
+
+	assert.NotEqual(t, []string{"refreshed_test"}, configFile.GetSectionList())
+	err = FileRefresh()
+	assert.NoError(t, err)
+	assert.Equal(t, []string{"refreshed_test"}, configFile.GetSectionList())
+}