doc: report project metadata update time (#286)

tests/thirdparty/metadata_test.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"flag"
 	"testing"
+	"time"
 
 	"github.com/mmcloughlin/avo/internal/github"
 	"github.com/mmcloughlin/avo/internal/test"
@@ -50,6 +51,10 @@ func TestSuiteFileMetadata(t *testing.T) {
 		}
 	}
 
+	if *update {
+		s.MetadataLastUpdate = time.Now().UTC()
+	}
+
 	if err := StoreSuiteFile("suite.json", s); err != nil {
 		t.Fatal(err)
 	}