create-bootstrap

#!/usr/bin/env bash
#
# The `create-bootstrap` script searches a repository for smallish LFS files,
# combines them into larger LFS files, and adds them to a new orphan branch
# called `bootstrap`. In addition, the script adds a `boot` script to the
# orphan branch which splits the larger LFS files up, again.
#
# In order to leverage the Git LFS pack files, the Git user needs to get the
# `bootstrap` branch and run the `boot` script.
#
# Usage:
#   1. Clone your repository with the smallish LFS files
#   2. `cd` into the repository
#   3. Run this script
#
set -e

base_dir=$(cd "${0%/*}" && pwd)
# force=1;

function header {
	echo ""
	echo "##############################################################"
	echo "  $1"
	echo "##############################################################"
}

function error {
	echo "ERROR: $1"
	exit 1
}

if [ ! -d .git ]; then
	error "Looks like you are not in the root directory of a Git repository."
fi

if [ -z "$force" ] && git rev-parse --verify origin/bootstrap >/dev/null 2>&1; then
	error "Branch 'bootstrap' exists already. Please delete it!"
fi

default_branch=$(git rev-parse --abbrev-ref HEAD)
remote_url=$(git config --get remote.origin.url)
repo_name=${remote_url##*/}
repo_name=${repo_name%.git}

header "Ensure relevant Git LFS objects are present..."
git pull
git lfs pull
git submodule foreach --recursive git lfs pull
git \
	-c lfs.fetchrecentcommitsdays=0 \
	-c lfs.fetchrecentrefsdays=0 \
	-c lfs.fetchrecentremoterefs=false \
	-c lfs.pruneoffsetdays=0 \
	lfs prune
git submodule foreach --recursive git \
	-c lfs.fetchrecentcommitsdays=0 \
	-c lfs.fetchrecentrefsdays=0 \
	-c lfs.fetchrecentremoterefs=false \
	-c lfs.pruneoffsetdays=0 \
	lfs prune

header "1/4 Creating 'bootstrap' branch..."
git checkout --orphan bootstrap
git reset
git clean -fdx --force --quiet

header "2/4 Creating Git LFS pack files..."

# Copy LFS files of the submodule into the parent repo to make them
# part of the LFS packfile
if [ -e ./.git/modules ]; then
	find ./.git/modules -type d -path '*/lfs' -exec cp -rf {} .git/ \;
fi

# Find all LFS files smaller than 256MB and put them into tar files no
# larger than 256MB. Finally, print the number of total files added to
# the archives.
rm -rf pack
mkdir pack
lfs_pack_count=$(
	find ./.git/lfs/objects -type f |
	perl -ne '
		my $path = $_;
		chomp($path);
		my $size = -s $path;
		if ($batch_size + $size > 256*1024*1024 || !$batch_id) {
			$batch_id++;
			$batch_size = 0;
		}
		if ($path && $size < 256*1024*1024) {
			$total_count++;
			$batch_size += $size;
			$tar = "pack/lfs-objects-$batch_id.tar";
			`tar -rf $tar $path`;
		}
		print $total_count if eof();
	'
)
# Compress those tar files
gzip pack/*
git lfs track 'pack/lfs-objects-*.tar.gz'
git add pack/lfs-objects-*.tar.gz 2>/dev/null || true

# Boot entry point for Linux/MacOS (bash)
cp "$base_dir/boot" boot
perl -pi -e "s/default_branch/$default_branch/" boot
perl -pi -e "s/lfs_pack_count/$lfs_pack_count/" boot

# Boot entry point for Windows (cmd.exe)
cp "$base_dir/boot.bat" boot.bat

cat << EOF > README.md

## Bootstrap Branch

This branch is not related to the rest of the repository content.
The purpose of this branch is to bootstrap the repository quickly
using Git LFS pack files and setting useful defaults.

Bootstrap the repository with the following commands.

### Windows (cmd.exe)
\`\`\`
$ git clone $remote_url --branch bootstrap && $repo_name\\boot.bat
\`\`\`

### Linux/MacOS (bash):
\`\`\`
$ git clone $remote_url --branch bootstrap && ./$repo_name/boot
\`\`\`

EOF

# Note: We intentionally do not add the `.gitattributes` file here.
#       This ensures the Git LFS pack files are not downloaded during
#       the initial clone and only with the `boot` script.
git add README.md boot boot.bat

header "3/4 Uploading 'bootstrap' branch..."
git -c user.email="bootstrap@github.com" \
	-c user.name="Bootstrap Creator" \
	commit --quiet --message="Initial commit"
git push --force --set-upstream origin bootstrap

header "4/4 Done"
cat README.md