ui_test: require colon after command

[RalfJung]

Turns out we already use colons everywhere properly.

Also rename ui_test::comments to parser. I think that better describes its contents. :)

[oli-obk]

Ah oops. I know where we don't tho: with //~ style comments, after the ERROR part

[RalfJung]

Ah, I didn't even know we allow : there.
That would make the syntax without a level be //~:? That looks kind of odd...

[RalfJung]

@bors r+

[bors]

📌 Commit 2850db9 has been approved by RalfJung

It is now in the queue for this repository.

[bors]

⌛ Testing commit 2850db9 with merge 6bdc5d6...

[bors]

☀️ Test successful - checks-actions
Approved by: RalfJung
Pushing 6bdc5d6 to master...

[oli-obk]

Yea, maybe we should forbid //~ ERROR: asdfg and just require a space for consistency?

[RalfJung]

Or we have to require some kind of keyword for "match an arbitrary level please". That would be the more robust thing to do, it avoids a silent fallback.

[oli-obk]

At that point we can require the proper level name and add another //@ command that can forcibly increase the threshold for levels that need annotations (instead of just picking the lowest one of any of the existing annotations like we do now).

[RalfJung]

Yeah that would work as well.