Action-bot automated repository can be filled with GA commits, the script would delete GA commits in HEAD until the earliest commit not authored by GA.

delete-github-action-head-commits.sh

#!/bin/bash

# Usage: action-bot automated repository can be filled with GA commits,
#        the script would delete GA commits in HEAD until the earliest commit not authored by GA.
# Author: Vinfall
# License: CC0 (Public Domain)

# Define a function to delete commits authored by a specific email address
del_ga_commits() {
    # Define the email address of the author to be deleted
    author_email="action@github.com"

    # Get the HEAD of the current branch
    current_commit=$(git rev-parse HEAD)

    # Loop to find the first commit that is not authored by the specified email address
    while true; do
        # Get the author of the current commit
        commit_author=$(git log -1 --pretty=format:"%ae" "$current_commit")

        # If the author is not the specified email address, stop the loop
        if [ "$commit_author" != "$author_email" ]; then
            break
        fi

        # Get the parent commit of the current commit
        current_commit=$(git log -1 --pretty=%P "$current_commit")
        
        # If it has reached the earliest commit, stop the loop
        if [ -z "$current_commit" ]; then
            echo "No commits authored by GitHub Action in HEAD found, no need to delete."
            return
        fi
    done

    # Get the short version of the commit hash
    short_commit=$(git rev-parse --short=8 "$current_commit")

    # Prompt the user to confirm the operation
    echo "You are about to delete all commits from HEAD to commit $short_commit. Continue? [y/n] \c"
    read -r REPLY
    if [[ $REPLY =~ ^[Yy]$ ]]
    then
        # Reset the main branch to the specified commit
        git reset --hard "$current_commit"

        # Push the changes to the remote repository
        git push origin main --force
    else
        echo "Operation canceled."
    fi
}

# Call the function to delete commits authored by a specific email address
del_ga_commits

Updated to make it pass shellcheck.