cli: reset terminal using libreadline when quitting on signal (bgo #706118)

readline() makes changes to terminal and when it doesn't receive unix signals,
it has no chance to perform cleanups on exit. So we have to call its cleanup
functions manually on exit.

https://bugzilla.gnome.org/show_bug.cgi?id=706118

cli/src/connections.c

@@ -4307,6 +4307,8 @@ typedef struct {
 	int *rl_attempted_completion_over_x;
 	int *rl_completion_append_character_x;
 	const char **rl_completer_word_break_characters_x;
+	void (*rl_free_line_state_func) (void);
+	void (*rl_cleanup_after_signal_func) (void);
 } EditLibSymbols;
 
 static EditLibSymbols edit_lib_symbols;
@@ -4663,6 +4665,12 @@ load_cmd_line_edit_lib (void)
 	if (!g_module_symbol (module, "rl_completer_word_break_characters",
 	                      (gpointer) (&edit_lib_symbols.rl_completer_word_break_characters_x)))
 		goto error;
+	if (!g_module_symbol (module, "rl_free_line_state",
+	                      (gpointer) (&edit_lib_symbols.rl_free_line_state_func)))
+		goto error;
+	if (!g_module_symbol (module, "rl_cleanup_after_signal",
+	                      (gpointer) (&edit_lib_symbols.rl_cleanup_after_signal_func)))
+		goto error;
 
 	/* Set a pointer to an alternative function to create matches */
 	*edit_lib_symbols.rl_attempted_completion_function_x = (CPPFunction *) nmcli_editor_tab_completion;
@@ -4676,6 +4684,15 @@ error:
 	return NULL;
 }
 
+void
+nmc_cleanup_readline (void)
+{
+	if (edit_lib_symbols.rl_free_line_state_func)
+		edit_lib_symbols.rl_free_line_state_func ();
+	if (edit_lib_symbols.rl_cleanup_after_signal_func)
+		edit_lib_symbols.rl_cleanup_after_signal_func ();
+}
+
 static char *
 readline_x (const char *prompt)
 {

cli/src/connections.h

@@ -24,4 +24,6 @@
 
 NMCResultCode do_connections (NmCli *nmc, int argc, char **argv);
 
+void nmc_cleanup_readline (void);
+
 #endif /* NMC_CONNECTIONS_H */

cli/src/nmcli.c

@@ -284,6 +284,7 @@ signal_handling_thread (void *arg) {
 		case SIGINT:
 		case SIGQUIT:
 		case SIGTERM:
+			nmc_cleanup_readline ();
 			printf (_("\nError: nmcli terminated by signal %d."), signo);
 			exit (1);
 			break;