This makes no sense (from
https://gerrit.wikimedia.org/g/mediawiki/extensions/ConfirmEdit):
# cd mediawiki/extensions
# git clone ssh://gerrit.wikimedia.org:29418/mediawiki/extensions/ConfirmEdit
Cloning into 'ConfirmEdit'...
Permission denied (publickey).
fatal: Could not read from remote repository.
Please make sure you have the correct access rights
and the repository exists.