Deleting repos
To delete a project foo from gerrit simply move the repo out of the way on the server:
mv gerrit/git/foo.git remove.me/
Then rebuild the caches and check the project list:
ssh -p 29418 review.example.com gerrit flush-caches --cache project_list
ssh -p 29418 review.example.com gerrit ls-projects
Groups
While older versions hat a drop down box to select whether it's a ldap or system group you need to prefix groups with ldap/ in recent gerrit.
Retrigger a sync to a mirror
Retrigger the sync to a certain destination by adding any part of it's URL:
GERRIT=localhost
ssh -p 29418 $GERRIT gerrit plugin reload replication
ssh -p 29418 $GERRIT replication start --url foobar --all --wait