# MD043 - Required header structure

Tags: headers

Aliases: required-headers

Parameters: headers (array of string; default `null` for disabled)

This rule is triggered when the headers in a file do not match the array of
headers passed to the rule. It can be used to enforce a standard header
structure for a set of files.

To require exactly the following structure:

    # Head
    ## Item
    ### Detail

Set the `headers` parameter to:

    [
        "# Head",
        "## Item",
        "### Detail"
    ]

To allow optional headers as with the following structure:

    # Head
    ## Item
    ### Detail (optional)
    ## Foot
    ### Notes (optional)

Use the special value `"*"` meaning "one or more unspecified headers" and set
the `headers` parameter to:

    [
        "# Head",
        "## Item",
        "*",
        "## Foot",
        "*"
    ]

When an error is detected, this rule outputs the line number of the first
problematic header (otherwise, it outputs the last line number of the file).

Note that while the `headers` parameter uses the "## Text" ATX header style for
simplicity, a file may use any supported header style.