fix for programmable completion functions setting traps on signals that readline handles

builtins/trap.def

@@ -22,31 +22,35 @@ $PRODUCES trap.c
 
 $BUILTIN trap
 $FUNCTION trap_builtin
-$SHORT_DOC trap [-lp] [[arg] signal_spec ...]
+$SHORT_DOC trap [-lp] [[action] signal_spec ...]
 Trap signals and other events.
 
 Defines and activates handlers to be run when the shell receives signals
 or other conditions.
 
-ARG is a command to be read and executed when the shell receives the
-signal(s) SIGNAL_SPEC.  If ARG is absent (and a single SIGNAL_SPEC
+ACTION is a command to be read and executed when the shell receives the
+signal(s) SIGNAL_SPEC.  If ACTION is absent (and a single SIGNAL_SPEC
 is supplied) or `-', each specified signal is reset to its original
-value.  If ARG is the null string each SIGNAL_SPEC is ignored by the
+value.  If ACTION is the null string each SIGNAL_SPEC is ignored by the
 shell and by the commands it invokes.
 
-If a SIGNAL_SPEC is EXIT (0) ARG is executed on exit from the shell.  If
-a SIGNAL_SPEC is DEBUG, ARG is executed before every simple command.  If
-a SIGNAL_SPEC is RETURN, ARG is executed each time a shell function or a
-script run by the . or source builtins finishes executing.  A SIGNAL_SPEC
-of ERR means to execute ARG each time a command's failure would cause the
-shell to exit when the -e option is enabled.
+If a SIGNAL_SPEC is EXIT (0) ACTION is executed on exit from the shell.
+If a SIGNAL_SPEC is DEBUG, ACTION is executed before every simple command
+and selected other commands. If a SIGNAL_SPEC is RETURN, ACTION is
+executed each time a shell function or a script run by the . or source
+builtins finishes executing.  A SIGNAL_SPEC of ERR means to execute ACTION
+each time a command's failure would cause the shell to exit when the -e
+option is enabled.
 
 If no arguments are supplied, trap prints the list of commands associated
-with each signal.
+with each trapped signal in a form that may be reused as shell input to
+restore the same signal dispositions.
 
 Options:
   -l	print a list of signal names and their corresponding numbers
-  -p	display the trap commands associated with each SIGNAL_SPEC
+  -p	display the trap commands associated with each SIGNAL_SPEC in a
+		form that may be reused as shell input; or for all trapped
+		signals if no arguments are supplied
 
 Each SIGNAL_SPEC is either a signal name in <signal.h> or a signal number.
 Signal names are case insensitive and the SIG prefix is optional.  A