ui: provide feedback on file upload

[myitcv]

Related to #126, we should give some visual indication within a terminal that a file has been uploaded.

Consider:

There is no way of knowing (from looking at the terminal) whether we have clicked the upload block, or when it happened.

#126 discusses a means by which we can feedback which steps have been clicked, but I think we also need to feedback to the user in the terminal when this happens too.

The simplest way of achieving this would be to send a command to the target terminal once the upload has completed. However, given it logically doesn't make much sense to run a command, we can instead send a comment, something like:

# successfully uploaded /home/gopher/readme.txt

I suspect this will require some changes in the SDK, unless we want to move to a model of preguide generating the command/code blocks (which would give us a bit more flexibility here)

cc @marcosnils

[marcosnils]

This is already handled by #169

[myitcv]

I just tried out #169

• I clicked on a file block (which was successful) but that didn't result in any comment in the terminal
• I then killed PWD and attempted an upload, but that didn't result in an error notification

Would it be best for me to create separate issues for these?

[marcosnils]

Did you restart the site container after switching to this branch? Since this requires a different version of the SDK, you need to restart it so the _config.yml gets reloaded. If you can also validate that the SDK 0.0.7 is being used while testing this that would be much appreciated since there could be something missing here.

[myitcv]

I did... but let me just double check.

[myitcv]

Ah, it appears to be using v0.0.4.

[myitcv]

Switched to using v0.0.7, but still seeing the same behaviour as above. Let's go through tomorrow

[marcosnils]

Fixed #169