#!/usr/bin/env bash


function show_help_and_exit {
    echo -e "Usage\n\t$1 <master branch> <branch to merge>\n"
    exit 2
}

[[ $# -eq 2 ]] || show_help_and_exit

VIMDIFF=vimdiff

MASTER_BRANCH=$1
MERGE_FROM_BRANCH=$2

TEMP_DIR="/tmp/gitvimdiff"
TEMP_FILE="$TEMP_DIR/`date '+%H:%M:%S.%N'`"

MASTER_FILE="$TEMP_FILE.master"
TO_MERGE_FILE="$TEMP_FILE.to_merge"

CHANGED_FILES="`git diff "$MASTER_BRANCH" "$MERGE_FROM_BRANCH" --name-only`"

function cleanup_data {
    echo 'cleaning temporary directory..'
    rm -rf $TEMP_DIR
}

function bashtrap {
    cleanup_data
}

trap bashtrap INT

mkdir -p $TEMP_DIR 2> /dev/null

git checkout $MERGE_FROM_BRANCH &> /dev/null || exit 4
for file in $CHANGED_FILES
do
    echo -e "++++ $file ++++" >> $TO_MERGE_FILE
    if [[ -f $file ]]
    then
        cat $file >> $TO_MERGE_FILE
    fi
done

git checkout $MASTER_BRANCH &> /dev/null || exit 5
for file in $CHANGED_FILES
do
    echo -e "---- $file ----" >> $MASTER_FILE
    if [[ -f $file ]]
    then
        cat $file >> $MASTER_FILE
    fi
done

$VIMDIFF $MASTER_FILE $TO_MERGE_FILE

cleanup_data
exit 0