Add --skip-cert-check flag to zrepl configcheck to prevent checking cert files

It may be desirable to check that a config is valid without checking for
the existence of certificate files (e.g. when validating a config inside
a sandbox without access to the cert files).

This will be very useful for NixOS so that we can check the config file
at nix-build time (e.g. potentially without proper permissions to read cert
files for a TLS connection).

fixes https://github.com/zrepl/zrepl/issues/467
closes https://github.com/zrepl/zrepl/pull/587

client/configcheck.go

@@ -19,8 +19,9 @@ import (
 )
 
 var configcheckArgs struct {
-	format string
-	what   string
+	format        string
+	what          string
+	skipCertCheck bool
 }
 
 var ConfigcheckCmd = &cli.Subcommand{
@@ -29,6 +30,7 @@ var ConfigcheckCmd = &cli.Subcommand{
 	SetupFlags: func(f *pflag.FlagSet) {
 		f.StringVar(&configcheckArgs.format, "format", "", "dump parsed config object [pretty|yaml|json]")
 		f.StringVar(&configcheckArgs.what, "what", "all", "what to print [all|config|jobs|logging]")
+		f.BoolVar(&configcheckArgs.skipCertCheck, "skip-cert-check", false, "skip checking cert files")
 	},
 	Run: func(ctx context.Context, subcommand *cli.Subcommand, args []string) error {
 		formatMap := map[string]func(interface{}){
@@ -56,8 +58,16 @@ var ConfigcheckCmd = &cli.Subcommand{
 		}
 
 		var hadErr bool
+
+		parseFlags := config.ParseFlagsNone
+
+		if configcheckArgs.skipCertCheck {
+			parseFlags |= config.ParseFlagsNoCertCheck
+		}
+
 		// further: try to build jobs
-		confJobs, err := job.JobsFromConfig(subcommand.Config())
+		confJobs, err := job.JobsFromConfig(subcommand.Config(), parseFlags)
+
 		if err != nil {
 			err := errors.Wrap(err, "cannot build jobs from config")
 			if configcheckArgs.what == "jobs" {

client/migrate.go

@@ -129,7 +129,7 @@ func doMigrateReplicationCursor(ctx context.Context, sc *cli.Subcommand, args []
 	}
 
 	cfg := sc.Config()
-	jobs, err := job.JobsFromConfig(cfg)
+	jobs, err := job.JobsFromConfig(cfg, config.ParseFlagsNone)
 	if err != nil {
 		fmt.Printf("cannot parse config:\n%s\n\n", err)
 		fmt.Printf("NOTE: this migration was released together with a change in job name requirements.\n")