`cmark`’s pretty-printer matches our output pretty well, with a few differences:
- it puts a space between the fence and the info string for in code blocks;
- it prefers `-` over `*` for bulleted lists (as do I) and it indents them;
- it `\`-escapes certain chars very conservatively;
- it prefers indented/unfenced code blocks if there is no info string; and
- it prefers `*` over `_` (unlike any sane person).
This also shows how the change fixes a number of issues:
- fix2158-1.output.md also illustrates how this change fixes#1809;
- alias-many.output.md and input-parse-errors.output.md show how fenced
code blocks without an info string would use the beginning of the
content as the info string;
- transcripts-round-trip/main.output.md shows how output blocks for
generated `unison` stanzas (which could contain nested fenced blocks)
might not have long-enough fences; and
- error-messages.output.md and generic-parse-errors.output.md show how
Unison errors were reported on the wrong line number (and thus the
printed error lines were also incorrect).
Previously, we were very sloppy, sometimes using the Ord instance for things displayed to humans, when that is only sometimes kinda sorta what you want. Separating this out into its own class lets us be careful about this and handle it uniformly.
- The 'pure' case was implemented incorrectly
- Also fixed the implementation of putBytes, it was giving back a 'unit'
value that was actually a handle.
