The markdown file for the 2017-07-29 posting seems to be missing from the repo, because building the website using hakyll does not recreate the posting. Perhaps the html output file was added without adding the markdown source file. The markdown file is recreated by using
Commit aaff037 'Add atom feed' added code to generate the atom feed content in atom.xml, but did not include a link to the xml file in the main index.html file, which means that an RSS/ATOM reader cannot automatically discover the Atom feed when given the website address.
'pandoc /posts/2017-07-29-modularization/index.html -o yi-documentation/posts/2017-07-29-modularization.md' .
and then pruning some residual markups.