Script to properly mirror a git repository.

mirror.sh

#!/bin/sh

# 
# Author:   ethomson (Edward Thomson)
# Gist:     https://gist.github.com/ethomson/3e8e9cabf360917d52a689d57bcf1729
# Article:  https://edwardthomson.com/blog/mirroring_git_repositories.html
#
# TL;DR
# Hosting provider stores information about pull requests in special read-only references,
#   which cause errors when you want to mirror a repository the Github way.
# This script avoids this by only pulling necessary references.
#
# GitHub way to mirror a repository:
# https://docs.github.com/en/repositories/creating-and-managing-repositories/duplicating-a-repository#mirroring-a-repository
#

#set -eufo pipefail
set -euf

if [ "$#" -ne 2 ]; then
    echo "usage: $0 source_repo_url target_repo_url" >&2
    exit 1
fi

SOURCE_URL="$1"
TARGET_URL="$2"
WORKDIR="$(mktemp -d)"

echo "Cloning from ${SOURCE_URL} into ${WORKDIR}..."

git init --bare "${WORKDIR}"
cd "${WORKDIR}"

git config remote.origin.url "${SOURCE_URL}"
git config --add remote.origin.fetch '+refs/heads/*:refs/heads/*'
git config --add remote.origin.fetch '+refs/tags/*:refs/tags/*'
git config --add remote.origin.fetch '+refs/notes/*:refs/notes/*'
git config remote.origin.mirror true
git fetch --all

echo ""
echo "Cloned to ${WORKDIR}; pushing to ${TARGET_URL}"

git push --mirror "${TARGET_URL}"

echo ""
echo "Cleaning up temporary directory ${WORKDIR}..."

rm -rf "${WORKDIR}"

echo "Done."