git-mirror/git-mirror.sh

#!/bin/bash

# git-mirror: Mirror a git repo in leader-followers configuration
# Copyright © 2019-2022 Midgard
#
# This program is free software: you can redistribute it and/or modify it under the terms of the
# GNU Affero General Public License as published by the Free Software Foundation, either version 3
# of the License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without
# even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License along with this program.
# If not, see <http://www.gnu.org/licenses/>.

set -euo pipefail
IFS=$'\n'

tor=true
if [[ "$1" == "--notor" ]]; then
	tor=false
	shift 1
fi

if [[ $# -lt 3 ]]; then
	echo "Usage: $0 [--notor] <workdir> <leader> <follower...>"
	exit 1
fi

cd "$1"

leader="$2"
shift 2
followers=( "$@" )

echo "Working directory: $PWD"
echo "Leader remote:     $leader"
echo "Follower remotes:  ${followers[*]}" | tr '\n' ' '
echo; echo

if [[ $tor == true ]]; then
	torify git fetch --prune --multiple "$leader"
else
	git fetch --prune --multiple "$leader"
fi
git fetch --prune --multiple "${followers[@]}"
echo

echo "Leader remote information:"
git remote show -n "$leader"
echo
echo "Follower remotes information:"
git remote show -n "${followers[@]}"
echo

branches=( $(git show-ref | sed -n 's| refs/remotes/'"$leader"'/|\t|p') )
echo -e "${#branches[*]} branches at leader:"
echo "${branches[*]}"

IFS=$'\t'

up_to_date=( )
errors=( )

error() {
	tput bold
	tput setaf 1
	echo -n "XXX"
	tput sgr0
	echo " $1" >&2
	errors[${#errors[*]}]="$1"
}

ref_exists() {
	git show-ref --verify --quiet "$1"
}

is_ref_at_sha() {
	sha1="$(git show-ref --verify --hash "$1")"
	sha2="$2"
	[[ $sha1 == $sha2 ]]
}

for branchspec in "${branches[@]}"; do
	set $branchspec
	leader_sha="$1"
	branch="$2"
	if [ "$branch" = HEAD ]; then continue; fi

	for remote in "${followers[@]}"; do

		follower_ref="refs/remotes/$remote/$branch"

		msg=""
		if ! ref_exists "$follower_ref"; then
			msg="Creating $remote/$branch"
		elif ! is_ref_at_sha "$follower_ref" "$leader_sha"; then
			msg="Updating $remote/$branch"
		else
			up_to_date[${#up_to_date[*]}]="$remote/$branch"
		fi

		if [[ -n $msg ]]; then
			echo
			tput bold
			echo "$msg"
			tput sgr0

			git push "$remote" "+$leader_sha:refs/heads/$branch" || { error "$remote $branch: failed to push"; continue; }
		fi

	done
done

if [[ "${#up_to_date[*]}" -gt 0 ]]; then
	echo
	echo "Already up to date:"
	echo "${up_to_date[@]}"
fi

echo
if [[ "${#errors[*]}" -gt 0 ]]; then
	tput bold
	tput setaf 1
	echo "Errors:"
	tput sgr0
	tput bold
	for (( i=0; i < ${#errors[*]}; i++ )); do
		echo "${errors[$i]}"
	done
	tput sgr0

	exit 1
else
	echo "No errors."
fi