fix(cli): revert #21583 (#22000)

Relates to https://github.com/coder/internal/issues/1217

This reverts commit f799cba395.

@deansheather reported that this breaks ControlMaster.

Investigating alternative fixes to coder/internal#1217

cli/ssh_test.go

@@ -1122,107 +1122,6 @@ func TestSSH(t *testing.T) {
 		}
 	})
 
-	// This test ensures that the SSH session exits when the parent process dies.
-	t.Run("StdioExitOnParentDeath", func(t *testing.T) {
-		t.Parallel()
-
-		ctx, cancel := context.WithTimeout(context.Background(), testutil.WaitSuperLong)
-		defer cancel()
-
-		// sleepStart -> agentReady -> sessionStarted -> sleepKill -> sleepDone -> cmdDone
-		sleepStart := make(chan int)
-		agentReady := make(chan struct{})
-		sessionStarted := make(chan struct{})
-		sleepKill := make(chan struct{})
-		sleepDone := make(chan struct{})
-
-		// Start a sleep process which we will pretend is the parent.
-		go func() {
-			sleepCmd := exec.Command("sleep", "infinity")
-			if !assert.NoError(t, sleepCmd.Start(), "failed to start sleep command") {
-				return
-			}
-			sleepStart <- sleepCmd.Process.Pid
-			defer close(sleepDone)
-			<-sleepKill
-			sleepCmd.Process.Kill()
-			_ = sleepCmd.Wait()
-		}()
-
-		client, workspace, agentToken := setupWorkspaceForAgent(t)
-		go func() {
-			defer close(agentReady)
-			_ = agenttest.New(t, client.URL, agentToken)
-			coderdtest.NewWorkspaceAgentWaiter(t, client, workspace.ID).WaitFor(coderdtest.AgentsReady)
-		}()
-
-		clientOutput, clientInput := io.Pipe()
-		serverOutput, serverInput := io.Pipe()
-		defer func() {
-			for _, c := range []io.Closer{clientOutput, clientInput, serverOutput, serverInput} {
-				_ = c.Close()
-			}
-		}()
-
-		// Start a connection to the agent once it's ready
-		go func() {
-			<-agentReady
-			conn, channels, requests, err := ssh.NewClientConn(&testutil.ReaderWriterConn{
-				Reader: serverOutput,
-				Writer: clientInput,
-			}, "", &ssh.ClientConfig{
-				// #nosec
-				HostKeyCallback: ssh.InsecureIgnoreHostKey(),
-			})
-			if !assert.NoError(t, err, "failed to create SSH client connection") {
-				return
-			}
-			defer conn.Close()
-
-			sshClient := ssh.NewClient(conn, channels, requests)
-			defer sshClient.Close()
-
-			session, err := sshClient.NewSession()
-			if !assert.NoError(t, err, "failed to create SSH session") {
-				return
-			}
-			close(sessionStarted)
-			<-sleepDone
-			// Ref: https://github.com/coder/internal/issues/1289
-			// This may return either a nil error or io.EOF.
-			// There is an inherent race here:
-			// 1. Sleep process is killed -> sleepDone is closed.
-			// 2. watchParentContext detects parent death, cancels context,
-			//    causing SSH session teardown.
-			// 3. We receive from sleepDone and attempt to call session.Close()
-			// Now either:
-			// a. Session teardown completes before we call Close(), resulting in io.EOF
-			// b. We call Close() first, resulting in a nil error.
-			_ = session.Close()
-		}()
-
-		// Wait for our "parent" process to start
-		sleepPid := testutil.RequireReceive(ctx, t, sleepStart)
-		// Wait for the agent to be ready
-		testutil.SoftTryReceive(ctx, t, agentReady)
-		inv, root := clitest.New(t, "ssh", "--stdio", workspace.Name, "--test.force-ppid", fmt.Sprintf("%d", sleepPid))
-		clitest.SetupConfig(t, client, root)
-		inv.Stdin = clientOutput
-		inv.Stdout = serverInput
-		inv.Stderr = io.Discard
-
-		// Start the command
-		clitest.Start(t, inv.WithContext(ctx))
-
-		// Wait for a session to be established
-		testutil.SoftTryReceive(ctx, t, sessionStarted)
-		// Now kill the fake "parent"
-		close(sleepKill)
-		// The sleep process should exit
-		testutil.SoftTryReceive(ctx, t, sleepDone)
-		// And then the command should exit. This is tracked by clitest.Start.
-	})
-
 	t.Run("ForwardAgent", func(t *testing.T) {
 		if runtime.GOOS == "windows" {
 			t.Skip("Test not supported on windows")