Simple backup engine to git.

backup_functions.sh

# create a reference if it dosen't exist yet
function __ensure_create_backup_branch()
{
    branch_name=$1

    reason=$2
    if [[ "$reason" != "" ]]; then
        reason_flag="-m"
    fi

    if [[ "$1" != "" ]]; then
        git rev-parse --verify "$branch_name" > /dev/null 2>&1 || git update-ref "$reason_flag" "$reason" "$branch_name" HEAD
    fi
}

# save all changed files (includes non-tracked, but not ignored ones) into a commit
function __save_all()
{
    branch_name=$1
    GIT_INDEX_FILE=$(mktemp -u $(git rev-parse --git-dir)/backup_index_XXXX)
    export GIT_INDEX_FILE

    git ls-files -o -m -c --exclude-standard | git update-index --add --remove --refresh --ignore-submodules --stdin > /dev/null 2>&1
    tree=$(git write-tree)
    branch_tree=$(git cat-file -p $(git log -1 --format=format:%H "$branch_name") | grep tree | cut -d ' ' -f 2)
    if [[ "$tree" != "$branch_tree" ]]; then
        git update-ref -m "update backup" "$branch_name" $(git commit-tree "$tree" -p "$branch_name" -m "Backup created on $(date -I)") || echo "could not update $branch_name"
    fi
    rm "$GIT_INDEX_FILE"
}

# Print the current task management and crates a backup (use on PS1)
function _task_management()
{
    current_task=$(task)
    if [[ "$current_task" == "" ]]; then
        echo "<no task>"
    else
        echo "[$current_task]"
    fi

    git rev-parse --git-dir >/dev/null 2>&1
    if [[ $? -eq 0 ]] ; then (
        branch_name="$(__task_backup_ref)"
        __ensure_create_backup_branch "$branch_name" "Creating backup branch"
        __save_all $branch_name

    )& fi
}

export TASKFILE="$HOME/.current_task"

# select the current task
function task()
{
    if [[ "$1" != "" ]]; then
        echo $1 > $TASKFILE;
    fi

    if [[ -f "$TASKFILE" ]]; then
        head -n 1 "$TASKFILE"
    fi
}

# finish the current task
function end_task()
{
    rm "$TASKFILE"
}

# cleanup all but the current task
function cleanup_backup_tasks()
{
    git_dir=$(git rev-parse --git-dir 2> /dev/null)
    current_task=$(task)
    for backup_ref in $(ls $git_dir/refs/backup); do
        if [[ "$backup_ref" != "$current_task" ]]; then
            git update-ref -m "cleanup backup tasks" -d $(__task_backup_ref "$backup_ref")
        fi
    done
}