There is nothing in the JSON output of https://api.github.com/orgs/wikimedia/repos that indicates whether a Github repository has been forked but I excluded those forked repos in T186736. Lots of noise so identifying new repos will not be easy.

Code, basically:

wget -q "https://api.github.com/orgs/wikimedia/repos?page=1&per_page=100" -O githubwmf01.json
cat githubwmf*.json | jq -r '.[] | select(.description|values | contains("irror") | not).html_url' > githubrepos.tmp
cat githubrepos.tmp >> githubreposall.tmp
(repeat for all pages and all groups)
cat githubreposall.tmp | sort > githubrepos.txt
curl -s https://gitlab.com/Bitergia/c/Wikimedia/sources/raw/master/projects.json | jq -r '.Wikimedia.git[]' | grep "https://github.com/" | sort > bitergiarepos.txt
echo "=== New Github repos to potentially add to Bitergia (if not Gerrit mirrors):"
comm -23 githubrepos.txt bitergiarepos.txt

Maybe it's way easier to just index any and all repo on Github under the groups we're interested in.

There is nothing in the JSON output of https://api.github.com/orgs/wikimedia/repos that indicates whether a Github repository has been forked ...

Just wondering about that statement, can't the fork property, which is present for each repository, be used to determine whether the repository is a fork or not? 🤔

For the records (and complexity), T213246#6770339 has a list of repos mirrored from GitHub to Gerrit as of 20210122...