Disallow duplicate headings in the same document.
Headings in Markdown documents are often used in a variety ways:
- To generate in-document links
- To generate a table of contents
When generating in-document links, unique headings are necessary to ensure you can navigate to a specific heading. Generated tables of contents then use those links, and when there are duplicate headings, you can only link to the first instance.
This rule warns when it finds more than one heading with the same text, even if the headings are of different levels.
Examples of incorrect code:
# Hello world!
## Hello world!
Goodbye World!
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# Goodbye World!If you aren't concerned with autolinking heading or autogenerating a table of contents, you can safely disable this rule.