Script to backdate tags

After importing one of my projects from Arch, I wanted to add tags that indicated its major releases. Unfortunately, these tags for older releases would show up before the more recent releases in the gitweb output. I searched in vain for a way of backdating tags, and finally decided to make a script to do this for me. Here it is.

This may run into issues if someone uses the "\" character in their tag names, but I didn't want to bother fixing this until it was affirmed that this script would be considered generally useful.

#!/bin/sh # # git-backdate-tag: Change the date of an existing tag, replacing the # tag reference with the newly-generated tag object. # # Usage: git-backdate-tag TAG DATE

usage () {
    echo "Usage: git-backdate-tag TAG DATE"
}

if [ -n "$3" ]; then
    usage
    exit 1
elif [ -z "$2" ]; then
    usage
    exit 1
fi

# Set parameters tag="$1" date=$(date --date="$2" +%s)

if [ $? -ne 0 ]; then
    echo Could not parse date
    exit 1
fi

# Replace old date with new date
newtagobj=$(git cat-file tag "$tag" | \
    sed -r -e "s/^(tagger .+) ([^ \\n]+) ([^ \\n]+)\$/\1 $date \3/1" | \
    git mktag)

if [ $? -ne 0 ]; then
    echo Could not create replacement tag object
    exit 1
fi

# Set tag to new tag object git update-ref refs/tags/"$tag" $newtagobj