Compiletest's "abbreviated" output can be very misleading

[Aaron1011]

Under certain circumstances, compiletest will 'abbreviate' the output of tests:

rust/src/tools/compiletest/src/read2.rs

Line 52 in e100ec5

write!(&mut head, "\n\n<<<<<< SKIPPED {} BYTES >>>>>>\n\n", skipped).unwrap();

However, the <<<<<< SKIPPED {} BYTES >>>>>> can easily be missed. I spent quite a while trying to figure out how the incremental compilation system was getting into a certain state without hitting any debug! statements, only to find out that a large chunk of the output was getting discarded.

Ideally, we would remove this 'abbreviation' logic entirely, and just ensure that our tests don't produce too much output. If it's really necessary, then we should require tests to opt in to this behavior, and fail the test if abbreviation is required when the test hasn't explicitly opted in.