Deduplicate path separator duplicates

[philderbeast]

Fixes #10645, a small Windows gotcha missed with #10546.

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• Patches conform to the coding conventions.
• Any changes that could be relevant to users have been recorded in the changelog.
  • Is the change significant? If so, remember to add significance: significant in the changelog file.
• The documentation has been updated, if necessary.
• Manual QA notes have been included.
• Tests have been added. Yes, a doctest.

[geekosaur]

I'm confused: is the .md file a GitHub artifact, or did you really add two changelog.d entries?

[philderbeast]

I'm confused: is the .md file a GitHub artifact, or did you really add two changelog.d entries?

Thanks for catching that mistake of mine @geekosaur. I let the .md slip in. I rename locally to check the markdown preview. I've deleted that extra file now.

Can we use a .md extension for changelog.d entries?

[geekosaur]

changelog-d doesn't care; the only special name is config, where its own configuration is stored, and you can't use subdirectories. It might even be better to use the extension, since that way GitHub will also render it (although it will probably be confused by the YAML frontmatter).