Update tests.
Reason: it turns out that the native output generated by
pretty-simple isn't always readable by the native reader.
According to https://github.com/cdepillabout/pretty-simple/issues/99
it is not a design goal of the library that the rendered values
be readable using 'read'. This makes it unsuitable for our
purposes.
pretty-show is a bit slower and it uses 4-space indents
(non-configurable), but it doesn't have this serious drawback.
Previously we used our own homespun formatting. But this
produces over-long lines that aren't ideal for diffs in tests.
Easier to use something off-the-shelf and standard.
Closes#7580.
Performance is slower by about a factor of 10, but this isn't
really a problem because native isn't suitable as a serialization
format. (For serialization you should use json, because the reader
is so much faster than native.)
Previously, if a document contained two YAML metadata blocks
that set the same field, the conflict would be resolved in favor
of the first. Now it is resolved in favor of the second (due to
a change in pandoc-types).
This makes the behavior more uniform with other things in pandoc
(such as reference links and `--metadata-file`).
When multiple YAML metadata blocks are used, and two define
the same field, the value defined first takes precedence,
according to the manual. This was changed briefly in
ba3ee62323. This commit
reverts to the original behavior and adds a test case.
