man git-tag for info, the committer needs GPG set up so git tag -s works. Then you can use your own checkout. Be sure the checkouts are under your user id and you do the tagging as yourself instead of as root.
+You may need to set GPG_TTY to get GPG to work if it tries to run pinentry-curses. This is the line for bash, since that's quoted most often for this fix.