#!/bin/bash
# Author: Luis R. Rodriguez <mcgrof@gmail.com>
# Generates a range of diffs based on a git commit log
# There has to be an easier way to do this...
# License: GPL

if [[ $# -ne 2 ]]; then
	echo "Usage $0 <git-log-file> <patch-dir>"
	exit
fi
LOG=$1

if [[ ! -f $LOG ]]; then
	echo "Log file doesn't exist"
	exit
fi

DIR=$2
if [[ ! -d $DIR ]]; then
	mkdir -p $DIR
	if [[ $? -ne 0 ]]; then
		exit
	fi
fi

COUNT=`wc -l $LOG | awk '{print $1}'`
echo "Log has $COUNT commits, generating diffs..."
i=$COUNT
NUM_DIFFS=1

while [ $i -ne 0 ]; do 
	CURR_LINE=$i
	PREV_LINE=$((CURR_LINE-1))
	CURR_COMMIT=`head -${CURR_LINE} $LOG | tail -1`
	PREV_COMMIT=`head -${PREV_LINE} $LOG | tail -1`
	if [[ ! -n $PREV_COMMIT ]]; then
		echo "Done! $PREV_COMMIT"
		break
	fi
	echo "diff $CURR_COMMIT .. $PREV_COMMIT"
	git-log -p ${CURR_COMMIT}..${PREV_COMMIT} > $DIR/${NUM_DIFFS}.diff
	if [[ $NUM_DIFFS -eq 1 ]]; then
		cat $DIR/${NUM_DIFFS}.diff > $DIR/all.diff
	else
		cat $DIR/${NUM_DIFFS}.diff >> $DIR/all.diff
	fi
	let NUM_DIFFS=$NUM_DIFFS+1
	let i=$i-1
done