[mirror config] extra rsync options (#107)

* support "rsync_options" array in config

* add test for new options

* fix tests

worker/rsync_provider.go

@@ -13,6 +13,7 @@ type rsyncConfig struct {
 	name                                         string
 	rsyncCmd                                     string
 	upstreamURL, username, password, excludeFile string
+	extraOptions                                 []string
 	workingDir, logDir, logFile                  string
 	useIPv6, useIPv4                             bool
 	interval                                     time.Duration
@@ -65,6 +66,9 @@ func newRsyncProvider(c rsyncConfig) (*rsyncProvider, error) {
 	if c.excludeFile != "" {
 		options = append(options, "--exclude-from", c.excludeFile)
 	}
+	if c.extraOptions != nil {
+		options = append(options, c.extraOptions...)
+	}
 	provider.options = options
 
 	provider.ctx.Set(_WorkingDirKey, c.workingDir)