mu-server: restore readline-support

Restore readline support for `mu server' (but _only_ when readline is
found and when in tty mode)

lib/utils/mu-readline.hh

@@ -0,0 +1,54 @@
+/*
+** Copyright (C) 2020 Dirk-Jan C. Binnema <djcb@djcbsoftware.nl>
+**
+** This program is free software; you can redistribute it and/or modify it
+** under the terms of the GNU General Public License as published by the
+** Free Software Foundation; either version 3, or (at your option) any
+** later version.
+**
+** This program is distributed in the hope that it will be useful,
+** but WITHOUT ANY WARRANTY; without even the implied warranty of
+** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+** GNU General Public License for more details.
+**
+** You should have received a copy of the GNU General Public License
+** along with this program; if not, write to the Free Software Foundation,
+** Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+**
+*/
+#include <string>
+
+namespace Mu {
+
+/**
+ * Setup readline when available & on tty.
+ *
+ * @param histpath path to the history file
+ * @param max_lines maximum number of history to save
+ */
+void setup_readline(const std::string &histpath, size_t max_lines);
+
+/**
+ * Shutdown readline
+*
+ */
+void shutdown_readline();
+
+
+/**
+ * Read a command line
+ *
+ * @param do_quit recceives whether we should quit.
+ *
+ * @return the string read or empty
+ */
+std::string read_line(bool &do_quit);
+
+/**
+ * Save a line to history (or do nothing when readline is not active)
+ *
+ * @param line a line.
+ */
+void save_line(const std::string &line);
+
+} // namespace Mu