Improve help for -i flag

Author: dolmen

main.go

@@ -256,7 +256,11 @@ func _main() error {
 		packages:   map[string]string{},
 		onlySemVer: true,
 	}
-	flag.Var(&imports, "i", "* import package: [alias=]import-path\n* switch to Go module mode and import package: [alias=]import-path@version")
+	flag.Var(&imports, "i", ``+
+		"* import package local package from GOPATH:  [alias=]import-path\n"+
+		"* import package in Go module mode:          [alias=]import-path@version\n"+
+		"Once a version is mentioned, Go module mode is enabled globally."
+	)
 
 	var goimports string
 	flag.StringVar(&goimports, "goimports", "goimports", "goimports tool name, to use an alternate tool or just disable it.")