A block scalar whose only lines are blank never establishes a content
indentation, so its blank lines stayed in the leading-blank buffer and were
discarded when the scalar ended. `keep: |+` over a blank line then resolved to
the empty string rather than the line break keep chomping should preserve.
At stream end, flush the buffered blank lines as content wrapped in an
indent/dedent pair, so the parser builds a block scalar of those lines and
chomping applies: keep preserves the breaks, clip and strip trim them. Only
the stream-end case is handled, where no following line constrains token
ordering; an empty keep scalar before a sibling key is left for later.
Raises yaml-test-suite value-level conformance to 189/194 (97.4%) with the
parse-level and should-error rejection rates unchanged. 456 tests pass.
Mihaela M
2b3d95d214