Use pretty-simple to format native output.

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.)

1 files changed, 31 insertions, 2 deletions

diff --git a/test/command/5271.md b/test/command/5271.md
index 910ea5888..e80bc3468 100644
--- a/test/command/5271.md
+++ b/test/command/5271.md
@@ -7,6 +7,35 @@ abstract: |
   It consists of two paragraphs.
 ...
 ^D
-Pandoc (Meta {unMeta = fromList [("abstract",MetaBlocks [Para [Str "This",Space,Str "is",Space,Str "the",Space,Str "abstract."],Para [Str "It",Space,Str "consists",Space,Str "of",Space,Str "two",Space,Str "paragraphs."]])]})
-[]
+Pandoc
+  ( Meta
+    { unMeta = fromList
+      [
+        ( "abstract"
+        , MetaBlocks
+          [ Para
+            [ Str "This"
+            , Space
+            , Str "is"
+            , Space
+            , Str "the"
+            , Space
+            , Str "abstract."
+            ]
+          , Para
+            [ Str "It"
+            , Space
+            , Str "consists"
+            , Space
+            , Str "of"
+            , Space
+            , Str "two"
+            , Space
+            , Str "paragraphs."
+            ]
+          ]
+        )
+      ]
+    }
+  ) []
 ```