*: add --result-format=json format

This is far easier to parse than the default raw format, and provides
the full serialised result structure.

Signed-off-by: Aleksa Sarai <asarai@suse.de>

check.go

@@ -9,15 +9,16 @@ import (
 
 // Result of a Check
 type Result struct {
-	Failures []Failure // list of any failures in the Check
+	// list of any failures in the Check
+	Failures []Failure `json:"failures"`
 }
 
 // Failure of a particular keyword for a path
 type Failure struct {
-	Path     string
+	Path     string `json:"path"`
-	Keyword  string
+	Keyword  string `json:"keyword"`
-	Expected string
+	Expected string `json:"expected"`
-	Got      string
+	Got      string `json:"got"`
 }
 
 // String returns a "pretty" formatting for a Failure

cmd/gomtree/main.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"bytes"
+	"encoding/json"
 	"flag"
 	"fmt"
 	"log"
@@ -30,6 +31,14 @@ var formats = map[string]func(*mtree.Result) string{
 		}
 		return buffer.String()
 	},
+
+	"json": func(r *mtree.Result) string {
+		var buffer bytes.Buffer
+		if err := json.NewEncoder(&buffer).Encode(r); err != nil {
+			panic(err)
+		}
+		return buffer.String()
+	},
 }
 
 func main() {