client: Enable history file by default unless -r

Make -H take an argument.  Default it to ~/.empire_history, except in
-r restricted mode, where history is off unless you specify -H.
That's because restricted mode restricts the player's access to the
local system, and that includes the history file.  If you want to
grant access to a history file, you have to do so explicitly.

Thanks to the previous commit, there is no need to suppress saving to
~/.empire_history in the test suite.

Signed-off-by: Markus Armbruster <armbru@pond.sub.org>

man/empire.6

@@ -3,8 +3,9 @@
 empire \- Empire client
 .SH SYNOPSIS
 .B empire
-[\fB\-hHkruv\fP]
+[\fB\-hkruv\fP]
 [\fB\-2\fP \fIoutfile\fP]
+[\fB\-H\fP \fIhistfile\fP]
 [\fB\-s\fP \fI[host:]port\fP]
 [\fIcountry\fP
 [\fIpassword\fP]]
@@ -24,8 +25,10 @@ the thin veneer of civilization that hides the maniac within.
 .B \-h
 Help.  Print brief usage information and exit.
 .TP
-.B \-H
-Save readline command history to file.
+.BI \-H " histfile"
+Load command history from \fIhistfile\fP, and save it back.  Default
+is '~/.empire_history' without \fB\-r\fP, and none with \fB-r\fP.  You
+might want to protect your history file from prying eyes.
 .IP
 Only available when compiled the GNU \fBreadline\fP library.
 .TP
@@ -85,8 +88,8 @@ The filename for the \fBreadline\fP startup file, overriding the
 default of \fI~/.inputrc\fP (see \fBREADLINE\fP below).
 .SH READLINE
 When compiled with the GNU \fBreadline\fP library, the client supports
-fancy line editing and, with option \fB-H\fP, persistent history.  See
-the readline documentation for details.
+fancy line editing and persistent history.  See the readline
+documentation for details.
 .SH "SEE ALSO"
 \fIemp_server\fR(6), \fIreadline\fR(3).
 .SH FILES