add --no-startup-message flag

cmd/root.go

@@ -1,7 +1,6 @@
 package cmd
 
 import (
-	"github.com/containrrr/watchtower/pkg/filters"
 	"os"
 	"os/signal"
 	"strconv"
@@ -11,6 +10,7 @@ import (
 	"github.com/containrrr/watchtower/internal/actions"
 	"github.com/containrrr/watchtower/internal/flags"
 	"github.com/containrrr/watchtower/pkg/container"
+	"github.com/containrrr/watchtower/pkg/filters"
 	"github.com/containrrr/watchtower/pkg/notifications"
 	t "github.com/containrrr/watchtower/pkg/types"
 	"github.com/robfig/cron"
@@ -123,14 +123,14 @@ func Run(c *cobra.Command, names []string) {
 		log.Fatal(err)
 	}
 
-	if err := runUpgradesOnSchedule(filter); err != nil {
+	if err := runUpgradesOnSchedule(c, filter); err != nil {
 		log.Error(err)
 	}
 
 	os.Exit(1)
 }
 
-func runUpgradesOnSchedule(filter t.Filter) error {
+func runUpgradesOnSchedule(c *cobra.Command, filter t.Filter) error {
 	tryLockSem := make(chan bool, 1)
 	tryLockSem <- true
 
@@ -156,7 +156,10 @@ func runUpgradesOnSchedule(filter t.Filter) error {
 		return err
 	}
 
+	if noStartupMessage, _ := c.PersistentFlags().GetBool("no-startup-message"); !noStartupMessage {
 		log.Info("Starting Watchtower and scheduling first run: " + cron.Entries()[0].Schedule.Next(time.Now()).String())
+	}
+
 	cron.Start()
 
 	// Graceful shut-down on SIGINT/SIGTERM

docs/notifications.md

@@ -18,6 +18,7 @@ The types of notifications to send are set by passing a comma-separated list of
 ## Settings
 
 - `--notifications-level` (env. `WATCHTOWER_NOTIFICATIONS_LEVEL`): Controls the log level which is used for the notifications. If omitted, the default log level is `info`. Possible values are: `panic`, `fatal`, `error`, `warn`, `info` or `debug`.
+- `--no-startup-message` (env. `WATCHTOWER_NOTIFICATION_NO_STARTUP_MESSAGE`): Prevents watchtower from sending a startup message.
 
 ## Available services
 

internal/flags/flags.go

@@ -123,6 +123,12 @@ func RegisterNotificationFlags(rootCmd *cobra.Command) {
 		viper.GetString("WATCHTOWER_NOTIFICATIONS_LEVEL"),
 		"The log level used for sending notifications. Possible values: panic, fatal, error, warn, info or debug")
 
+	flags.BoolP(
+		"no-startup-message",
+		"",
+		viper.GetBool("WATCHTOWER_NOTIFICATION_NO_STARTUP_MESSAGE"),
+		"Prevents watchtower from sending a startup message")
+
 	flags.StringP(
 		"notification-email-from",
 		"",