tramp smashes my .bash_history file

[Skip Montanaro]

I'm using tramp 2.0.35 on XEmacs 21.5 beta 9.  Even though I see this code
in (tramp-open-connection-setup-interactive-shell):

  (tramp-message
   9 "Waiting 30s for `HISTFILE=$HOME/.tramp_history; HISTSIZE=1'")
  (tramp-send-command-internal multi-method method user host
                               "HISTFILE=$HOME/.tramp_history; HISTSIZE=1")

on one of the remote systems on which I edit files (a Solaris 8 system
running Bash 2.03.0(1)-release) I find no .tramp_history file, but see all
manner of tramp-related shell commands in ~/.bash_history.  On another
system (Mandrake 8.1 running Bash 2.05.1(1)-release) I set

  HISTIGNORE=*tramp_exit_status*:*tramp_file_attributes*
  export HISTIGNORE

in ~/.bash_profile and set

    HISTSIZE=1000
    export HISTSIZE
in /etc/profile.  That machine has a .tramp_history file containing (as
expected) a single line.  I don't set HISTFILE on either system.  I checked 

    ~/.bash_profile
    ~/.bashrc
    ~/.profile
    /etc/profile

for HIST* commands on both systems.

I must be missing something (hopefully obvious), but what?

Thanks,

-- 
Skip Montanaro
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