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, 28 insertions, 1 deletions

diff --git a/test/command/5619.md b/test/command/5619.md
index 776d57acc..dbf82c822 100644
--- a/test/command/5619.md
+++ b/test/command/5619.md
@@ -6,5 +6,32 @@
 
   The caption. Here's what piggybacking on caption would look like {#fig:1}
 ^D
-[Para [Image ("test",[],[("width","1in")]) [Str "The",Space,Str "caption.",Space,Str "Here's",Space,Str "what",Space,Str "piggybacking",Space,Str "on",Space,Str "caption",Space,Str "would",Space,Str "look",Space,Str "like",Space,Str "{#fig:1}"] ("img1.jpg","fig:")]]
+[ Para
+  [ Image
+    ( "test", [], [ ( "width", "1in" ) ] )
+    [ Str "The"
+    , Space
+    , Str "caption."
+    , Space
+    , Str "Here's"
+    , Space
+    , Str "what"
+    , Space
+    , Str "piggybacking"
+    , Space
+    , Str "on"
+    , Space
+    , Str "caption"
+    , Space
+    , Str "would"
+    , Space
+    , Str "look"
+    , Space
+    , Str "like"
+    , Space
+    , Str "{#fig:1}"
+    ]
+    ( "img1.jpg", "fig:" )
+  ]
+]
 ```