pandoc/test/command/shift-heading-level-by.md

```
% pandoc --shift-heading-level-by 1 -t native -s
---
title: My title
...

# First heading

## Second
^D
Pandoc
  Meta
    { unMeta =
        fromList
          [ ( "title"
            , MetaInlines [ Str "My" , Space , Str "title" ]
            )
          ]
    }
  [ Header
      2
      ( "first-heading" , [] , [] )
      [ Str "First" , Space , Str "heading" ]
  , Header 3 ( "second" , [] , [] ) [ Str "Second" ]
  ]
```

```
% pandoc --shift-heading-level-by -1 -t native -s
---
title: Old title
...

# First heading

## Second

# Another top-level heading
^D
Pandoc
  Meta
    { unMeta =
        fromList
          [ ( "title"
            , MetaInlines [ Str "First" , Space , Str "heading" ]
            )
          ]
    }
  [ Header 1 ( "second" , [] , [] ) [ Str "Second" ]
  , Para
      [ Str "Another"
      , Space
      , Str "top-level"
      , Space
      , Str "heading"
      ]
  ]
```