Add default path for config file

Previously, the path to the config file had to be passed on the command line.
This commit adds a sensible default so that this is no longer necessary.

As the mechanism for setting the channel plugin dir based on libexecdir from
the Makefile is already there, the same was used for sysconfdir, even though
that should always be /etc for our packaging needs.

Dockerfile

@@ -23,4 +23,4 @@ RUN adduser -u 1000 -H -D -G $username $username
 USER $username
 
 EXPOSE 5680
-CMD ["/usr/sbin/icinga-notifications", "--config", "/etc/icinga-notifications/config.yml"]
+CMD ["/usr/sbin/icinga-notifications"]

Makefile

@@ -15,7 +15,7 @@ all:
 	mkdir -p build
 	go build \
 		-o build/ \
-		-ldflags "-X '$(pkg).LibExecDir=$(libexecdir)'" \
+		-ldflags "-X '$(pkg).LibExecDir=$(libexecdir)' -X '$(pkg).SysConfDir=$(sysconfdir)'" \
 		./cmd/icinga-notifications
 	go build -o build/channel/ ./cmd/channel/...
 

cmd/icinga-notifications/main.go

@@ -26,7 +26,7 @@ func main() {
 	var configPath string
 	var showVersion bool
 
-	flag.StringVar(&configPath, "config", "", "path to config file")
+	flag.StringVar(&configPath, "config", internal.SysConfDir+"/icinga-notifications/config.yml", "path to config file")
 	flag.BoolVar(&showVersion, "version", false, "print version")
 	flag.Parse()
 
@@ -43,11 +43,6 @@ func main() {
 		return
 	}
 
-	if configPath == "" {
-		_, _ = fmt.Fprintln(os.Stderr, "missing -config flag")
-		os.Exit(1)
-	}
-
 	err := daemon.LoadConfig(configPath)
 	if err != nil {
 		_, _ = fmt.Fprintln(os.Stderr, "cannot load config:", err)

internal/paths.go

@@ -1,6 +1,7 @@
 package internal
 
-// This variable exists to allow overwriting the path using `go build -ldflags "-X ...", see Makefile.
+// These variables exist to allow overwriting the paths using `go build -ldflags "-X ...", see Makefile.
 var (
 	LibExecDir = "/usr/libexec"
+	SysConfDir = "/etc"
 )