#!/bin/bash

set -euo pipefail

fatal() {
	echo "$@" >&2
	exit 1
}

main() {

	local target="$1"

	# Validate target hg repo
	if [[ ! -d $target/.hg ]] ; then
		fatal "${1} not a hg repo"
	fi

	# Convert to absolute path
	{
		cd "$target"
		target=$(pwd)
	}

	(
		cd "$target"
		if [[ $(hg status | wc -l) -ne 0 ]] ; then
			fatal "${1}: uncommited files, abandoning"
		fi

		if hg id | fgrep -q '+' ; then
			fatal "${1}: uncommitted changes, abandoning"
		fi

		# Create 'master' hg bookmark, if there isn't one already
		if ! hg bookmark | fgrep master ; then
			hg bookmark master
		fi
	)

	# Use mercurial-git plugin to convert to bare repo in /tmp/
	local gitdir=$(mktemp -d /tmp/hg2git.XXXXXXXX)

	(
		cd "$gitdir"
		git init --bare
	)

	(
		cd "$target"
		hg push "$gitdir"
	)

	# Move into place
	local backupdir="$target.hg-converted-$(date -Iseconds)"
	mv "$target" "$backupdir"

	mkdir -p "${target}"

	mv "$gitdir/" "$target/.git"

	# Reconstruct working directory
	(
		cd "$target"
		git config --local --bool core.bare false
		git checkout master
	)

	# Copy over excluded files from the working directory
	# (add trailing slash to source path)
	rsync -avr "${backupdir}/" "$target" --exclude=.git --exclude=.hg

	(
		cd "$target"

		# Remove hgtags file
		if [[ -f ./.hgtags ]] ; then
			git rm ./.hgtags
			git commit -m "hg-git: remove old .hgtags file"
		fi

		# Convert hgignore->gitignore (partial)
		if [[ -f ./.hgignore ]] ; then
			git mv .hgignore .gitignore
			sed -i '/^mode:/d' .gitignore
			# leave in uncommitted state for further fixups
		fi
	)
}

main "$@"