Git rewrite tags as commits. Squash everything but preserve tags.

git-rewrite-tags-as-commits

#!/bin/bash

ORIGINAL_BRANCH="main"
NEW_BRANCH="new-history"
START_COMMIT="84eafe059aa3059d2e3db260a2248deae7502c57"
NEW_TAG_PREFIX="v2-"

git checkout -b ${NEW_BRANCH} ${START_COMMIT}

# Loop through every tag on the ORIGINAL_BRANCH
for TAG in $(git tag --merged ${ORIGINAL_BRANCH})
do
    echo "----------------------------------------------------------------------------------------------------"
    echo "Re-creating ${TAG}"
    echo "----------------------------------------------------------------------------------------------------"
    
    # Retrieve all the metadata for the commit
    # https://git-scm.com/docs/git-show#Documentation/git-show.txt-emsem
    MSG=$(git show -s --pretty=tformat:%s ${TAG})
    # https://git-scm.com/docs/git-show#Documentation/git-show.txt-emaiem
    DATE=$(git show -s --pretty=tformat:%ai ${TAG})
    # https://git-scm.com/docs/git-show#Documentation/git-show.txt-emanem
    AUTHOR_NAME=$(git show -s --pretty=tformat:%an ${TAG})
    # https://git-scm.com/docs/git-show#Documentation/git-show.txt-emaeem
    AUTHOR_EMAIL=$(git show -s --pretty=tformat:%ae ${TAG})

    # Create a new commit command using the metadata. Ensure the author and committer are set.
    COMMIT="git -c user.name=\"${AUTHOR_NAME}\" -c user.email=\"${AUTHOR_EMAIL}\" commit --allow-empty -m \"${MSG}\" --date \"${DATE}\""

    # Remove all files except hidden
    rm -r `ls`

    # Checkout all files at tag
    git checkout ${TAG} -- .

    # Stage all files
    git add .

    # Commit all files
    bash -c "${COMMIT}"

    # Create tag
    git tag "${NEW_TAG_PREFIX}${TAG}"
done