etcdctl: allow move-leader to connect to multiple endpoints with TLS

Re-opening closed PR etcd-io#11775 which was originaly authored by benmoss.

The mustClientForCmd function is responsible for parsing environment
variables and flags into configuration data. A change was made in etcd-io#9382
to call Fatal if a flag is provided multiple times. This means that we
cannot call the mustClientForCmd function more than once,
since it will think that flags parsed the first time are now
being redefined and error out.

Some people have commented about this in etcd-io#8380 but I don't think
there's an open issue for it.

etcdctl/ctlv3/command/move_leader_command.go

@@ -43,7 +43,8 @@ func transferLeadershipCommandFunc(cmd *cobra.Command, args []string) {
 		cobrautl.ExitWithError(cobrautl.ExitBadArgs, err)
 	}
 
-	c := mustClientFromCmd(cmd)
+	cfg := clientConfigFromCmd(cmd)
+	c := cfg.mustClient()
 	eps := c.Endpoints()
 	c.Close()
 
@@ -53,7 +54,6 @@ func transferLeadershipCommandFunc(cmd *cobra.Command, args []string) {
 	var leaderCli *clientv3.Client
 	var leaderID uint64
 	for _, ep := range eps {
-		cfg := clientConfigFromCmd(cmd)
 		cfg.endpoints = []string{ep}
 		cli := cfg.mustClient()
 		resp, serr := cli.Status(ctx, ep)

tests/e2e/ctl_v3_move_leader_test.go

@@ -28,25 +28,34 @@ import (
 )
 
 func TestCtlV3MoveLeaderSecure(t *testing.T) {
-	testCtlV3MoveLeader(t, *newConfigTLS())
+	testCtlV3MoveLeader(t, withCfg(*newConfigTLS()))
+	testCtlV3MoveLeader(t, withCfg(*newConfigTLS()), withFlagByEnv())
 }
 
 func TestCtlV3MoveLeaderInsecure(t *testing.T) {
-	testCtlV3MoveLeader(t, *newConfigNoTLS())
+	testCtlV3MoveLeader(t, withCfg(*newConfigNoTLS()))
+	testCtlV3MoveLeader(t, withCfg(*newConfigNoTLS()), withFlagByEnv())
 }
 
-func testCtlV3MoveLeader(t *testing.T, cfg etcdProcessClusterConfig) {
+func testCtlV3MoveLeader(t *testing.T, opts ...ctlOption) {
 	BeforeTest(t)
 
-	epc := setupEtcdctlTest(t, &cfg, true)
+	ret := ctlCtx{
+		t:           t,
+		cfg:         *newConfigAutoTLS(),
+		dialTimeout: 7 * time.Second,
+	}
+	ret.applyOpts(opts)
+
+	epc := setupEtcdctlTest(t, &ret.cfg, true)
 	defer func() {
 		if errC := epc.Close(); errC != nil {
 			t.Fatalf("error closing etcd processes (%v)", errC)
 		}
 	}()
 
 	var tcfg *tls.Config
-	if cfg.clientTLS == clientTLS {
+	if ret.cfg.clientTLS == clientTLS {
 		tinfo := transport.TLSInfo{
 			CertFile:      certPath,
 			KeyFile:       privateKeyPath,
@@ -94,11 +103,13 @@ func testCtlV3MoveLeader(t *testing.T, cfg etcdProcessClusterConfig) {
 		cfg:         *newConfigNoTLS(),
 		dialTimeout: 7 * time.Second,
 		epc:         epc,
+		envMap:      map[string]struct{}{},
 	}
 
 	tests := []struct {
 		prefixes []string
 		expect   string
+
 	}{
 		{ // request to non-leader
 			cx.prefixArgs([]string{cx.epc.EndpointsV3()[(leadIdx+1)%3]}),