Add "configtest" CLI command. (#1230)

Co-authored-by: Kristoffer Dalby <kristoffer@dalby.cc>
Fixes https://github.com/juanfont/headscale/issues/1229

CHANGELOG.md

@@ -4,6 +4,8 @@
 
 ### changes
 
+- Adding "configtest" CLI command.
+
 ## 0.20.0 (2023-02-03)
 
 ### changes

cmd/headscale/cli/configtest.go

@@ -0,0 +1,22 @@
+package cli
+
+import (
+	"github.com/spf13/cobra"
+	"github.com/rs/zerolog/log"
+)
+
+func init() {
+	rootCmd.AddCommand(configTestCmd)
+}
+
+var configTestCmd = &cobra.Command{
+	Use:   "configtest",
+	Short: "Test the configuration.",
+	Long:  "Run a test of the configuration and exit.",
+	Run: func(cmd *cobra.Command, args []string) {
+		_, err := getHeadscaleApp()
+		if err != nil {
+			log.Fatal().Caller().Err(err).Msg("Error initializing")
+		}
+	},
+}