Record folder-specific history in `.dir_bash_history`

mycd.sh

function cd_dir_history()
{
    OLDPWD="$PWD"
    echo "# $(date) $USER -> $@" >> "$HISTFILE"

    command cd "$@"

    # If this directory is writable then write to directory-based history file
    # otherwise write history in the usual home-based history file.
    touch "$PWD/.dir_bash_history" 2>/dev/null \
        && export HISTFILE="$PWD/.dir_bash_history" \
        || export HISTFILE="$HOME/.bash_history";

    echo "# $(date) $USER <- $OLDPWD" >> "$HISTFILE"
}

# Replace the regular `cd` command.
alias cd="cd_dir_history"

# Initial shell opened.
export HISTFILE="$PWD/.dir_bash_history"

# Timestamp all history entries.
export HISTTIMEFORMAT="%h/%d - %H:%M:%S "
export HISTCONTROL=ignoredups:erasedups
export HISTSIZE=1000000
export HISTFILESIZE=1000000

shopt -s histappend # Append, no clearouts.
shopt -s histverify # Edit a recalled history line before executing.
shopt -s histreedit # Reedit a history substitution line if it failed.

# Save the history after each command finishes.
# (and keep any existing PROMPT_COMMAND settings).
export PROMPT_COMMAND="history -a; history -c; history -r; $PROMPT_COMMAND"