Rename a git tag old to new:

git tag new old
git tag -d old
git push origin :refs/tags/old
git push --tags

The colon in the push command removes the tag from the remote repository. If you don't do this, git will create the old tag on your machine when you pull.

-- source http://stackoverflow.com/a/5719854/695454

start new:

tmux

start new with session name:

tmux new -s myname