Update the local repository
git fetch origin master
Create a local branch with origin/master as its start point.
git checkout -b revert$RANDOM origin/master
Find the SHA1 of the commit you want to revert
git log origin/master
Create a revert commit.
git revert <SHA1>
Upload it to Gerrit.
git cl upload
Land the revert in origin/master.
git cl land
Delete the local revert branch.
git checkout --detach && git branch -D @{-1}