Duplicate publications in multilingual site

[mythsmith]

Describe the bug

Each language should only show its own publication. Instead, I see one publication entry for each configured language.

To Reproduce

1. Follow the instructions to set up a starter-academic example site.
2. Copy all content/* into subfolder content/en.
3. Copy content/en to content/it
4. Rename content/it/publication/example to example2
5. Set defaultContentLanguageInSubdir: true in config.toml
6. Add to languages.toml:

it:
  languageCode: it-IT
  contentDir: content/it

See https://github.com/mythsmith/wowchemy-bug

Expected behavior

Each language should only show its own publication. Instead, I see 2 for each language: both en/example and it/example2.

In a more complex setup, with tens of publications, I got a lot more confusion, like publications being linked to /en/it/name, instead of /it/name, and missing from the additional language search page. This bug report is an attempt to find out the root cause.

Technical details:

• Link to your GitHub project: https://github.com/mythsmith/wowchemy-bug
• Wowchemy Version (from your go.mod): v0.0.0-20210226164504-3952bfc85cee
• Hugo Version (run hugo version): Hugo Static Site Generator v0.80.0-792EF0F4/extended linux/amd64 BuildDate: 2020-12-31T13:46:18Z
• Browser/OS: not applicable
• Wowchemy Template (e.g. Academic): Acedemic