Ability to run in standalone mode

* In addition to the server mode, it is now possible to run the
    program in standalone mode. In that mode, the updates selector and
    force flag will be read from the command line, the updates will be
    executed immediately, and the program will exit.
  * Client mode ready to be implemented

main.go

@@ -12,6 +12,16 @@ type (
 	tCliFlags struct {
 		// The path to the configuration file.
 		cfgFile string
+		// Mode to run as. May be either standalone (executes an update
+		// then quits), client (connects to the server and requests an
+		// update) or server (runs the server in the foreground).
+		runMode string
+		// The selector to use when running the updates. Only meaningful
+		// if running in client or standalone mode.
+		selector string
+		// Whether updates should be forced. Only meaningful if running
+		// in client or standalone mode.
+		force bool
 		// Quiet mode. Will disable logging to stderr.
 		quiet bool
 		// The log level.
@@ -40,13 +50,28 @@ func parseCommandLine() tCliFlags {
 	var help bool
 	flags := tCliFlags{}
 
-	golf.StringVarP(&flags.cfgFile, 'c', "config", "/etc/fetch-certificates.yml", "Path to the configuration file.")
+	golf.StringVarP(&flags.cfgFile, 'c', "config", "/etc/fetch-certificates.yml",
-	golf.StringVarP(&flags.logFile, 'f', "log-file", "", "Path to the log file.")
+		"Path to the configuration file.")
-	golf.StringVarP(&flags.logGraylog, 'g', "log-graylog", "", "Log to Graylog server (format: <host>:<port>).")
+	golf.BoolVarP(&flags.force, 'f', "force", false,
-	golf.BoolVarP(&help, 'h', "help", false, "Display command line help and exit.")
+		"Force update of selected certificates. Only meaningful in "+
-	golf.StringVarP(&flags.logLevel, 'L', "log-level", "info", "Log level to use.")
+			"client or standalone mode.")
-	golf.BoolVarP(&flags.quiet, 'q', "quiet", false, "Quiet mode; prevents logging to stderr.")
+	golf.StringVarP(&flags.logFile, 'F', "log-file", "",
-	golf.BoolVarP(&flags.logSyslog, 's', "syslog", false, "Log to local syslog.")
+		"Path to the log file.")
+	golf.StringVarP(&flags.logGraylog, 'g', "log-graylog", "",
+		"Log to Graylog server (format: <host>:<port>).")
+	golf.BoolVarP(&help, 'h', "help", false,
+		"Display command line help and exit.")
+	golf.StringVarP(&flags.logLevel, 'l', "log-level", "info",
+		"Log level to use.")
+	golf.StringVarP(&flags.runMode, 'm', "mode", "standalone",
+		"Mode of execution (client/server/[standalone])")
+	golf.BoolVarP(&flags.quiet, 'q', "quiet", false,
+		"Quiet mode; prevents logging to stderr.")
+	golf.BoolVarP(&flags.logSyslog, 's', "syslog", false,
+		"Log to local syslog.")
+	golf.StringVarP(&flags.selector, 'u', "update", "*",
+		"LDAP DN of the certificate to select, or '*' to update all "+
+			"certificates.")
 
 	golf.Parse()
 	if help {
@@ -116,21 +141,33 @@ func (state *tServerState) mainLoop() {
 }
 
 func main() {
-	// This utility will load its configuration then start listening on
-	// a UNIX socket. It will be handle messages that can :
-	// - stop the program,
-	// - update the configuration,
-	// - check a single entry for replacement,
-	// - check all entries for replacement.
-	// Both check commands include a flag that will force replacement.
-
 	flags := parseCommandLine()
 	err := configureLogging(flags)
 	if err != nil {
 		log.WithField("error", err).Fatal("Failed to configure logging.")
 	}
 
+	if flags.runMode == "server" {
 		server := initServer(flags.cfgFile)
 		defer server.destroy()
 		server.mainLoop()
+		return
+	}
+
+	cfg, err := LoadConfiguration(flags.cfgFile)
+	if err != nil {
+		log.WithField("error", err).Fatal("Failed to load initial configuration.")
+	}
+	if flags.runMode == "standalone" {
+		result := executeUpdate(&cfg, flags.selector, flags.force)
+		if result {
+			log.Debug("Update successful")
+		} else {
+			log.Fatal("Update failed")
+		}
+	} else if flags.runMode == "client" {
+		panic("CLIENT MODE NOT IMPLEMENTED") // FIXME
+	} else {
+		log.WithField("mode", flags.runMode).Fatal("Unknown execution mode.")
+	}
 }