Clear the current line when activating in terminal

[edvilme]

Ensures that the current terminal line is cleared before the command for activation is passed to the terminal. Before, it would interrupt user input, resulting in corrupted commands like: git pu\n, which not only produces the wrong command, but can lead to unsafe execution.

This occurs on the legacy (de)activation, due to users:

• Having setting erminal.integrated.shellIntegration.enabled = false
• Using a shell that does not support shell integration
• Using slower machines, or remote SSH, and the shell integration timeout elapsing before the handshake.

[edvilme]

Ref #1375

[edvilme]

Would be superseded by #962 but this consider the case for using the legacy activation

[eleanorjboyd]

going to defer this to @anthonykim1 to make a decision since this is his area of expertise. I am inclined to say we hold on this as we get the terminal experiments out and the stuff anthony has been working on since that should address the same problem

[anthonykim1]

Thanks for the PR :)

I don't think we should do this, as clearing line is pretty aggressive compared to ^c keyboard interrupt which is part of shell integration's executeCommand.
Even with the keyboard interrupt there has been much complains about how "aggressive" the behavior is.

Big downside of clearing line is that user may be typing something but clearing before the explicit activation command would result in that typing experience "disappearing".
Aside from user typing, we would also have to assume that other extensions may be trying to send command upon launch of terminal so clearing would be effectively "undo"-ing their behavior as well.

Keyboard interrupt behavior is more expected as it shows what user was typing (or extension sending command) before the ^C is inserted.

As far as shell integration, majority of our users are on it, and it's been the default ever since its introduction.
It's what also powers copilot terminal experience, so we'd want to focus on shell integration enabled experience.

In case auto-injection fails, we do provide way for manual installation here : https://code.visualstudio.com/docs/terminal/shell-integration#_manual-installation

It's great that you called out #962 since we're planning roll shell startup as the default once env extension is fully rolled out.