compat/terminal: factor out echo-disabling

By moving the echo-disabling code to a separate function, we can
implement OS-specific versions of it for non-POSIX platforms.

Signed-off-by: Erik Faye-Lund <kusmabite@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

compat/terminal.c

@@ -14,6 +14,7 @@ static void restore_term(void)
 		return;
 
 	tcsetattr(term_fd, TCSAFLUSH, &old_term);
+	close(term_fd);
 	term_fd = -1;
 }
 
@@ -24,6 +25,27 @@ static void restore_term_on_signal(int sig)
 	raise(sig);
 }
 
+static int disable_echo(void)
+{
+	struct termios t;
+
+	term_fd = open("/dev/tty", O_RDWR);
+	if (tcgetattr(term_fd, &t) < 0)
+		goto error;
+
+	old_term = t;
+	sigchain_push_common(restore_term_on_signal);
+
+	t.c_lflag &= ~ECHO;
+	if (!tcsetattr(term_fd, TCSAFLUSH, &t))
+		return 0;
+
+error:
+	close(term_fd);
+	term_fd = -1;
+	return -1;
+}
+
 char *git_terminal_prompt(const char *prompt, int echo)
 {
 	static struct strbuf buf = STRBUF_INIT;
@@ -34,24 +56,9 @@ char *git_terminal_prompt(const char *prompt, int echo)
 	if (!fh)
 		return NULL;
 
-	if (!echo) {
-		struct termios t;
-
-		if (tcgetattr(fileno(fh), &t) < 0) {
-			fclose(fh);
-			return NULL;
-		}
-
-		old_term = t;
-		term_fd = fileno(fh);
-		sigchain_push_common(restore_term_on_signal);
-
-		t.c_lflag &= ~ECHO;
-		if (tcsetattr(fileno(fh), TCSAFLUSH, &t) < 0) {
-			term_fd = -1;
-			fclose(fh);
-			return NULL;
-		}
+	if (!echo && disable_echo()) {
+		fclose(fh);
+		return NULL;
 	}
 
 	fputs(prompt, fh);