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Gitit's README file claims that page metadata may contain a keyword for categories which is followed by "a space or comma separated list". Notice or.
However function splitCategories in Network.Gitit.Util converts commas, periods, colons and semicolons to spaces and then splits the string.
So either the function should match documentation and split only on spaces or commas or, alternatively, documentation should be amended so as to make clear that different delimiters are possible and practically interchangeable.
I came across this behaviour when trying to use comma-separated items consisting of multiple words as category names. For example: categories: John Doe, Jane Doe is parsed as four categories and not as two as I expected.
categories: John Doe, Jane Doe
[Added later] Moreover, Network.Gitit.Page.hs claims in comments that "[t]he categories in the @categories@ field should be separated by spaces. Commas will be treated as spaces", contradicting documentation.