Add support for Ctrl-C to interrupt commands, and add multi-line capa… - #613

The summary message for commit 14e8dac is far longer than it should be. This template is what all Git commit messages should follow.

Your notes in the PR description are what should be the body of the commit message. Keep in mind that PRs are not permanent (they exist only on GitHub); only the Git commit messages are actually tied to the project. Be as descriptive as you can with your commit messages.

Just reiterating information from phone conversations; we have a couple things going on here:

• We should not sleep our ReadLine thread as this breaks shell responsiveness (keys are updated only when the thread wakes up; not when the user hit a key)
• Console.KeyAvailable appears broken in that it is only returning true when Enter was hit; at which point all the previous buffered key strokes came through
• TreatControlCAsInput is not implemented and would be a pain to get implemented; if it were implemented, we'd have to be really careful to enable and disable it appropriately so that the handler is called appropriately during pipeline execution
• It would not be totally odd for Esc to handle clearing multi-line input, as it already clears single-line input; I understand it is different from Windows, and that is acceptable as the alternatives are not viable

I'm not too concerned about responsiveness. I did a quick web search, and the fastest one could type is about 12 strokes a second, or about 83 milliseconds between strokes. If I change sleep to 80 milliseconds, it should be plenty to keep up with fastest typist.

As for second item, I assume a fix is forth coming. Any estimate on when they will fix that? I currently don't see this problem. Have they released the broken patch, or will wait for the new fix before releasing everything?

Since the resolution of this PR will not be immediate, I will take changes associated with multi-line out of this PR, and create a separate PR for it.

You don't see the problem because the pinned packages are before any of the changes. The fix is already up in dotnet/corefx#6619; I didn't catch it because we weren't using Console.KeyAvailable.

Thanks George Fleming (@palladia).

New push that includes most changes per Andy comments. Ctrl-C works great, and with 80 msec sleep, there's no apparent lag.

Will re-test after CoreFx #6619 is pulled into our build.

I'd prefer to wait until after we've merged in the new packages, so we can test before merging.

No problem.

Tested on latest .NET updates... this performs very oddly.

TreatControlCAsInput has been implemented in dotnet/corefx#6669, which should be available in build 23908 (which I'll get us updated to ASAP).