The purpose is to have valid EPUB ebooks of my Omnivore articles.
You need to have Calibre and omnivoreql installed (as a system python
package since calibre could only import it that way - or there might be
other ways, that I did not investigated yet.
You have to set (e.g. in your .bashrc an environment variable that points
to a file that has (only) your Omnivore API key, e.g.:
export OMNICALAPIKEY="$HOME/API.key"
With this set up, you can run the CLI provided by Calibre to get a nicely formatted (and valid) EPUB file:
ebook-convert o.recipe Omnivore-$(date +%F).epub \
--output-profile kindle \
--smarten-punctuation \
--change-justification justify \
--title "Omnivore archive" \
--toc-title "Table of Contents" \
--remove-paragraph-spacing-indent-size 1.3