Configuration file for geoipupdate is actually optional

CHANGELOG.md

@@ -6,6 +6,8 @@
   such as HTTP2 INTERNAL_ERROR.
 * `HTTPReader` no longer retries on HTTP errors and therefore
   `retryFor` was removed from `NewHTTPReader`.
+* Now `geoipupdate` doesn't requires the user to specify the config file
+  even if all the other arguments are set via the environment variables.
 
 ## 6.1.0 (2024-01-09)
 

cmd/geoipupdate/args.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"errors"
 	"log"
 	"os"
 
@@ -23,6 +24,13 @@ func getArgs() *Args {
 		confFileDefault = value
 	}
 
+	// Set the default config file only if it exists.
+	// Othwerwise, geoipupdate requires the user to specify the config file
+	// even if all the other arguments are set via the environment variables.
+	if _, err := os.Stat(confFileDefault); errors.Is(err, os.ErrNotExist) {
+		confFileDefault = ""
+	}
+
 	configFile := flag.StringP(
 		"config-file",
 		"f",