#!/bin/bash
#
# Describe submodules in repository, optionally per commit
# 
# Usage:
# submodule-describe <path-to-repo> [<commit>]
# 
# Output: 
# <hash>	<path>	<url>
# <hash>	<path>	<url>
# 
# everything separated with tabs

# Safe mode
set -euo pipefail
IFS=$'\n\t'

# get config file for specific commit
function getConfigFile() {
	git --no-pager show $commit:.gitmodules
}

# parse submodule file from file
function parseSectionNames(){
	git config -f $1 --list --name-only | grep '^submodule.' | cut -d. -f2 | sort | uniq
}

# generate line for single submodule
function generateDescription(){
	cfgFile=$1
	section=$2

	path=$(git config -f $cfgFile --get submodule.$section.path)
	url=$(git config -f $cfgFile --get submodule.$section.url)
	hash=$(git ls-tree -l $commit -- $path | cut -d' ' -f3)

	printf "%s\t%s\t%s\n" $hash $path $url
}




# Grab varriables
repodir=$1
commit=${2:-HEAD}

# Go to repo directory
oldPwd=$(pwd)
cd $repodir

# Are there any submodules registered? 
test 0 -eq `git ls-tree $commit -- .gitmodules | wc -l` && exit 0

tmpfile=$(mktemp)

getConfigFile $repodir $commit > $tmpfile
for section in $(parseSectionNames $tmpfile)
do
	generateDescription $tmpfile $section
done


# Cleanup
rm $tmpfile
# Go back home
cd $oldPwd