fix: fly volume fork --require-unique-zone should be default (#3955)

Checking `flag.IsSpecified` makes its default false.

internal/command/volumes/fork.go

@@ -105,11 +105,6 @@ func runFork(ctx context.Context) error {
 		machinesOnly = fly.Pointer(flag.GetBool(ctx, "machines-only"))
 	}
 
-	var requireUniqueZone *bool
-	if flag.IsSpecified(ctx, "require-unique-zone") {
-		requireUniqueZone = fly.Pointer(flag.GetBool(ctx, "require-unique-zone"))
-	}
-
 	region := flag.GetString(ctx, "region")
 
 	var attachedMachineImage string
@@ -131,7 +126,7 @@ func runFork(ctx context.Context) error {
 	input := fly.CreateVolumeRequest{
 		Name:                name,
 		MachinesOnly:        machinesOnly,
-		RequireUniqueZone:   requireUniqueZone,
+		RequireUniqueZone:   fly.Pointer(flag.GetBool(ctx, "require-unique-zone")),
 		SourceVolumeID:      &vol.ID,
 		ComputeRequirements: computeRequirements,
 		ComputeImage:        attachedMachineImage,

test/preflight/fly_volume_test.go

@@ -35,6 +35,7 @@ func TestVolume(t *testing.T) {
 	t.Run("Extend", WithParallel(testVolumeExtend))
 	t.Run("List", WithParallel(testVolumeLs))
 	t.Run("CreateFromDestroyedVolSnapshot", WithParallel(testVolumeCreateFromDestroyedVolSnapshot))
+	t.Run("Fork", WithParallel(testVolumeFork))
 }
 
 func testVolumeExtend(t *testing.T) {
@@ -122,6 +123,21 @@ func testVolumeLs(t *testing.T) {
 	}, 5*time.Minute, 10*time.Second)
 }
 
+func testVolumeFork(t *testing.T) {
+	f := testlib.NewTestEnvFromEnv(t)
+	appName := f.CreateRandomAppMachines()
+
+	var original *fly.Volume
+	j := f.Fly("vol create --json --app %s --region %s --yes foobar", appName, f.PrimaryRegion())
+	j.StdOutJSON(&original)
+
+	var fork *fly.Volume
+	j = f.Fly("vol fork --json --app %s --region %s %s", appName, f.PrimaryRegion(), original.ID)
+	j.StdOutJSON(&fork)
+
+	assert.NotEqual(t, original.Zone, fork.Zone, "forked volume should be in a different zone")
+}
+
 func testVolumeCreateFromDestroyedVolSnapshot(tt *testing.T) {
 	t := testLogger{tt}