Fix ONCE environment variable ignorance

Hi there,

Here's the MR to fix the issue I have faced with ONCE environment variable being ignored, when executed via Docker.

One important note: this changes docker-compose-watcher (or, in fact, compose-updater) default value of once to false, so that it would be possible to remove -once=0 from Dockerfile, but still keeping the old behavior:

CMD ["docker-compose-watcher", "-once=0", "-printSettings"]

The reason of removing this argument from CMD above is rather simple: due to code structure command line arguments takes precedence over environment variables, which I think is the right way to go. However, keeping -once=0 will prevent ability to override behavior of passing environment variable ONCE to Docker.

Basically, this MR makes everyone happy.

Few other small things irrelevant to original issue comes as a bonus.

Author: dieselburner

Dockerfile

@@ -38,4 +38,4 @@ RUN \
     curl -SLf https://github.com/docker/compose/releases/download/v${COMPOSE_VERSION}/docker-compose-linux-${DOWNLOAD_ARCH} -o /usr/local/lib/docker/cli-plugins/docker-compose && \
     chmod +x /usr/local/lib/docker/cli-plugins/docker-compose
 COPY --from=builder /go/src/app/main /usr/local/bin/docker-compose-watcher
-CMD ["docker-compose-watcher", "-once=0", "-printSettings"]
+CMD ["docker-compose-watcher", "-printSettings"]

src/settings.go

@@ -5,7 +5,6 @@ import (
 	"log"
 	"os"
 	"strconv"
-	"strings"
 )
 
 // Settings holds the program runtime configuration
@@ -34,7 +33,7 @@ func ReadSettings() {
 	s.boolFlagEnv(&s.Dry, "dry", "DRY", false, "dry run: check and pull, but don't restart")
 	s.boolFlagEnv(&s.Help, "help", "HELP", false, "print usage instructions")
 	s.int64FlagEnv(&s.Interval, "interval", "INTERVAL", 60, "interval in minutes between runs")
-	s.boolFlagEnv(&s.Once, "once", "ONCE", true, "run once and exit, do not run in background")
+	s.boolFlagEnv(&s.Once, "once", "ONCE", false, "run once and exit, do not run in background")
 	s.boolFlagEnv(&s.PrintSettings, "printSettings", "PRINT_SETTINGS", false, "print used settings")
 	s.stringFlagEnv(&s.UpdateLog, "updateLog", "UPDATE_LOG", "", "update log file")
 	//s.boolFlagEnv(&s.CompleteStop, "completeStop", "COMPLETE_STOP", false, "Restart all services in docker-compose.yml (even unmanaged) after a new image is pulled")
@@ -51,23 +50,32 @@ func ReadSettings() {
 func (settings *Settings) boolFlagEnv(p *bool, name string, env string, value bool, usage string) {
 	flag.BoolVar(p, name, value, usage+" (env "+env+")")
 	val := os.Getenv(env)
-	if (val != "") && (val != "0") && (strings.ToLower(val) != "false") {
-		*p = true
+	if val != "" {
+		b, err := strconv.ParseBool(val)
+		if err != nil {
+			log.Fatal(err)
+		}
+		*p = b
 	}
 }
 
 func (settings *Settings) int64FlagEnv(p *int64, name string, env string, value int64, usage string) {
 	flag.Int64Var(p, name, value, usage+" (env "+env+")")
-	if os.Getenv(env) != "" {
-		i, _ := strconv.ParseInt(os.Getenv(env), 10, 0)
+	val := os.Getenv(env)
+	if val != "" {
+		i, err := strconv.ParseInt(val, 10, 0)
+		if err != nil {
+			log.Fatal(err)
+		}
 		*p = i
 	}
 }
 
 func (settings *Settings) stringFlagEnv(p *string, name string, env string, value string, usage string) {
 	flag.StringVar(p, name, value, usage+" (env "+env+")")
-	if os.Getenv(env) != "" {
-		*p = os.Getenv(env)
+	val := os.Getenv(env)
+	if val != "" {
+		*p = val
 	}
 }