Add a --config option to point to config files in custom locations.

go/cmd/zeus/zeus.go

@@ -32,7 +32,7 @@ func main() {
 				slog.TraceLogger = slog.NewTraceLogger(tracefile)
 				Args = Args[1:]
 			} else {
-				fmt.Printf("Could not open trace file %s", Args[1])
+				fmt.Printf("Could not open trace file %s\n", Args[1])
 				return
 			}
 		case "--file-change-delay":
@@ -46,6 +46,14 @@ func main() {
 			} else {
 				execManPage("zeus")
 			}
+		case "--config":
+			_, err := os.Stat(Args[1])
+			if err != nil {
+				fmt.Printf("Config file doesn't exist: %s (%e)\n", Args[1], err)
+				return
+			}
+			config.ConfigFile = Args[1]
+			Args = Args[1:]
 		case "--version":
 			printVersion()
 			return
@@ -55,6 +63,10 @@ func main() {
 		execManPage("zeus")
 	}
 
+	// Don't confuse the master by sending *full* args to it; just those that are
+	// not zeus-specific.
+	config.Args = Args
+
 	if generalHelpRequested(Args) {
 		execManPage("zeus")
 	} else if Args[0] == "help" {

go/config/config.go

@@ -13,7 +13,7 @@ import (
 
 var Args = os.Args[1:]
 
-const configFile string = "zeus.json"
+var ConfigFile string = "zeus.json"
 
 type config struct {
 	Command string
@@ -89,7 +89,7 @@ func readConfigFileOrDefault(configFile string) ([]byte, error) {
 func parseConfig() (c config) {
 	var conf config
 
-	contents, err := readConfigFileOrDefault(configFile)
+	contents, err := readConfigFileOrDefault(ConfigFile)
 	if err != nil {
 		zerror.ErrorConfigFileInvalidJson()
 	}

man/src/zeus.ronn

@@ -3,7 +3,7 @@ zeus(1) -- boot rails in under a second
 
 ## SYNOPSIS
 
-`zeus` [--no-color] [--log FILE] [--file-change-delay TIME] COMMAND [ARGS]
+`zeus` [--no-color] [--log FILE] [--file-change-delay TIME] [--config PATH] COMMAND [ARGS]
 
 ## DESCRIPTION
 
@@ -56,6 +56,9 @@ See `https://github.com/burke/zeus/blob/master/docs/overview.md`
   and restart processes only after this deadline expires. The argument
   must be parseable by time.ParseDuration. The default delay is 300ms.
 
+* `--config` path:
+  Read from the given JSON config file.
+
 ## BUILTIN COMMANDS
 
 * [zeus start(1)][zeus-start]: