--dump not working

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Hi, thank you for hastyscribe. I'm using linux binary 1.12.1 downloaded from the release page. I want to dump CSS styles, so I used ./hastyscribe --output-file=/path/file.html --dump=styles file.markdown but hastyscribe didn't dump anything to the current directory and displayed its usage message instead (no additional error message). I tried with different values for --dump, with only --dump, with option(s) before and after the markdown files, without markdown filename but nothing worked. Just usage information is output.

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Thank you.