nixos-render-docs: extend md_make_code

add the ability to set the info string for a newly created fenced code
block, and a flag to always emit a fenced block. the commonmark
converter will need this to faithfully recreate fenced and indented code
blocks.

pkgs/tools/nix/nixos-render-docs/src/nixos_render_docs/md.py

@@ -27,10 +27,10 @@ _md_escape_table = {
 def md_escape(s: str) -> str:
     return s.translate(_md_escape_table)
 
-def md_make_code(code: str) -> str:
+def md_make_code(code: str, info: str = "", multiline: Optional[bool] = None) -> str:
     # for multi-line code blocks we only have to count ` runs at the beginning
     # of a line, but this is much easier.
-    multiline = '\n' in code
+    multiline = multiline or info != "" or '\n' in code
     longest, current = (0, 0)
     for c in code:
         current = current + 1 if c == '`' else 0
@@ -38,7 +38,7 @@ def md_make_code(code: str) -> str:
     # inline literals need a space to separate ticks from content, code blocks
     # need newlines. inline literals need one extra tick, code blocks need three.
     ticks, sep = ('`' * (longest + (3 if multiline else 1)), '\n' if multiline else ' ')
-    return f"{ticks}{sep}{code}{sep}{ticks}"
+    return f"{ticks}{info}{sep}{code}{sep}{ticks}"
 
 AttrBlockKind = Literal['admonition', 'example']