jpictl: introduce --config-file/-f as alternative to scanning m/

Signed-off-by: Alejandro Mery <amery@jpi.io>

cmd/jpictl/config.go

@@ -1,11 +1,25 @@
 package main
 
-import "git.jpi.io/amery/jpictl/pkg/cluster"
+import (
+	"os"
+
+	"darvaza.org/core"
+
+	"git.jpi.io/amery/jpictl/pkg/cluster"
+)
+
+const (
+	// DefaultConfigFile is read if -f/--config-file isn't specified.
+	// If it doesn't exist, m/ will be scanned
+	DefaultConfigFile = "cloud.yaml"
+)
 
 // Config describes the repository
 type Config struct {
 	Base   string
 	Domain string
+
+	ConfigFile string
 }
 
 var cfg = &Config{
@@ -14,9 +28,32 @@ var cfg = &Config{
 }
 
 // LoadZones loads all zones and machines in the config directory
+// or file
 func (cfg *Config) LoadZones(resolve bool) (*cluster.Cluster, error) {
+	// try config file first
+	zones, err := cluster.NewFromConfig(cfg.ConfigFile,
+		cluster.ResolvePublicAddresses(resolve),
+		cluster.WithLogger(log),
+	)
+
+	switch {
+	case err == nil:
+		// file was good
+		return zones, nil
+	case !os.IsNotExist(err) || cfg.ConfigFile != DefaultConfigFile:
+		// file was bad
+		return nil, core.Wrapf(err, "NewFromConfig(%q)", cfg.ConfigFile)
+	}
+
+	// default file doesn't exist. scan instead.
 	return cluster.NewFromDirectory(cfg.Base, cfg.Domain,
 		cluster.ResolvePublicAddresses(resolve),
 		cluster.WithLogger(log),
 	)
 }
+
+func init() {
+	rootCmd.PersistentFlags().
+		StringVarP(&cfg.ConfigFile, "config-file", "f",
+			DefaultConfigFile, "config file (JSON or YAML)")
+}