Where is the commit-msg in gerrit?

[vista...@gmail.com]

When push the commit to gerrit for review , sometime  the error of "miss change-id" happen 

And take this command "gitdir=$(git rev-parse --git-dir);scp -p -P 29418 xxx@yyy:hooks/commit-msg ${gitdir}/hooks/" to solve the problem

Where is the script of commit-msg in server of gerrit? 

Thanks