Hack to replace a git annotated/signed tag with a newly-named, signed one.

git-retag

#!/bin/sh

# Name    : git-retag
# Created : 2010-12-11
# Author  : cwilper
# Purpose : Replaces an existing git annotated or signed tag with a new, 
#           signed one, using the original tagger name, email address, 
#           tag date, and 1-line message.
#
# Usage: git-retag oldname newname
#
# WARNING: This is a quick and dirty script with no absolutely no error
#          checking -- be careful! It works for me, but might break 
#          stuff for you. Back up your repository before using, etc..
#
# NOTICE : This script was written to help clean up old tags during a
#          migration to git.  It is not intended, though possible, to
#          use on a repository people have already pulled from.
#          If you do use it on such a repository, but sure to 
#          "git push --tags" and have people "git fetch -t"
#
# Q: Why not just use git tag -f newname oldname as suggested
#    in the git-tag manpage?
#
# A: Because it doesn't really rewrite the internal name
#    of the annotated tag object.  If you use git tag -f,
#    you will still see evidence of the old name when using 
#    'git describe' or 'git show'.  In addition, tools that look at 
#    the internal name (like git bash completion) will still show the
#    old name, which sucks.
#

name=`git show $1 | head -n 2 | tail -n 1 | sed 's/^Tagger: \(.*\) <\(.*\)>/\1/'`
email=`git show $1 | head -n 2 | tail -n 1 | sed 's/^Tagger: \(.*\) <\(.*\)>/\2/'`
date=`git show $1 | head -n 3 | tail -n 1 | sed 's/^Date:   \(.*\)/\1/'`
comment=`git show $1 | head -n 5 | tail -n 1`
commit=`git show $1 | grep '^commit ........................................$' | sed 's/commit //'`

export GIT_COMMITTER_NAME="$name"
export GIT_COMMITTER_EMAIL="$email"
export GIT_COMMITTER_DATE="$date"

git tag -d $1
git tag -asm "$comment" $2 $commit

unset GIT_COMMITTER_NAME
unset GIT_COMMITTER_EMAIL
unset GIT_COMMITTER_DATE