Merge pull request #351 from github/check-flag

cli: --check-flag

Author: Shlomi Noach

go/cmd/gh-ost/main.go

@@ -115,8 +115,13 @@ func main() {
 	stack := flag.Bool("stack", false, "add stack trace upon error")
 	help := flag.Bool("help", false, "Display usage")
 	version := flag.Bool("version", false, "Print version & exit")
+	checkFlag := flag.Bool("check-flag", false, "Check if another flag exists/supported. This allows for cross-version scripting. Exits with 0 when all additional provided flags exist, nonzero otherwise. You must provide (dummy) values for flags that require a value. Example: gh-ost --check-flag --cut-over-lock-timeout-seconds --nice-ratio 0")
+
 	flag.Parse()
 
+	if *checkFlag {
+		return
+	}
 	if *help {
 		fmt.Fprintf(os.Stderr, "Usage of gh-ost:\n")
 		flag.PrintDefaults()