ChunkMatches: drop trailing newline (#709)
I'd like to start taking advantage of the NumContextLines option, but have been running into an issue where, if context lines were to extend past the end of the file, we get the trailing newline at the end of the file.
This is not desirable because the empty slice after a trailing newline is not treated as a "line" by any editor, so when we split on newlines, an empty line is shown to the user. By the time we're splitting on newlines, we do not know whether or not we're at the end of the file, so we cannot know whether we can trim that trailing newline, or whether it is, correctly, an empty line that should be rendered.
This is really annoying stuff that bites us elsewhere as well (searcher, syntax highlighter). It might be nice to unify the definitions of "what is a line" in some library, but for now, I'll be happy with "don't return an extra line."