Add shared report format flag

internal/commandmeta/metadata_test.go

@@ -5,7 +5,7 @@ import "testing"
 func TestReportingFlagsAreBooleanAndReturnedIndependently(t *testing.T) {
 	flags := ReportingFlags()
 	want := []string{"quiet", "verbose", "debug", "progress"}
-	if len(flags) != len(want) {
+	if len(flags) != len(want)+1 {
 		t.Fatalf("reporting flags = %#v", flags)
 	}
 	for index, name := range want {
@@ -16,6 +16,13 @@ func TestReportingFlagsAreBooleanAndReturnedIndependently(t *testing.T) {
 			t.Errorf("%q is not recognized as a reporting flag", name)
 		}
 	}
+	if flags[4].Name != "format" || flags[4].Boolean || !IsReportingFlag("format") {
+		t.Fatalf("format metadata = %#v", flags[4])
+	}
+	flags[4].Completion.Choices[0].Value = "changed"
+	if ReportingFlags()[4].Completion.Choices[0].Value != "text" {
+		t.Fatal("caller mutation changed format choices")
+	}
 	flags[0].Name = "changed"
 	if ReportingFlags()[0].Name != "quiet" {
 		t.Fatal("caller mutation changed shared reporting metadata")