The current test DSL currently has no way to express being at the end of
a line, save for putting an explicit LF or CRLF inside the `#[|]#`. The
problem with this approach is that it can add unintended extra new lines
if used in conjunction with raw strings, which insert newlines for you.
This is a simple attempt to mitigate this problem. If there is an
explicit newline character at the end of the selection, and then it
is immediately followed by the same newline character at the right end
of the selection, this following newline is removed. This way, one can
express a cursor at the end of a line explicitly.
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