bash history in each writeable working directory

.bashrc

#!/bin/bash

# per-directory history
shopt -s histappend  # always append to history, don't replace
export PROMPT_COMMAND="builtin history -a;$PROMPT_COMMAND" # write to history file at every new prompt
export HISTTIMEFORMAT="%m/%d/%y %T "
alias cd='cd_with_local_history'
alias history='cat $HOME/.bash_history'
export HISTFILE="$PWD/.bash_cwd_history_$USER"
function cd_with_local_history()
{
     if [ -w "$@" ]
     then
        export HISTFILE="$PWD/.bash_cwd_history_$USER"
        builtin history -w # write the local history file 
        cat $HOME/.bash_history .bash_cwd_history_$USER > .bash_cat_history
        # preserve the global history file
        mv .bash_cat_history $HOME/.bash_history
        builtin cd "$@" # do actual cd
        export HISTFILE="$PWD/.bash_cwd_history_$USER"
        builtin history -c # clear memory
        builtin history -r #read from current histfile
      else
	export HISTFILE="$HOME/.bash_history"
        builtin cd "$@" # do actual cd
      fi
}