terminal: work around macos poll() bug

On macos the builtin "add -p" does not handle keys that generate
escape sequences because poll() does not work with terminals
there. Switch to using select() on non-windows platforms to work
around this.

Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

compat/terminal.c

@@ -92,6 +92,31 @@ static int enable_non_canonical(enum save_term_flags flags)
 	return disable_bits(flags, ICANON | ECHO);
 }
 
+/*
+ * On macos it is not possible to use poll() with a terminal so use select
+ * instead.
+ */
+static int getchar_with_timeout(int timeout)
+{
+	struct timeval tv, *tvp = NULL;
+	fd_set readfds;
+	int res;
+
+	if (timeout >= 0) {
+		tv.tv_sec = timeout / 1000;
+		tv.tv_usec = (timeout % 1000) * 1000;
+		tvp = &tv;
+	}
+
+	FD_ZERO(&readfds);
+	FD_SET(0, &readfds);
+	res = select(1, &readfds, NULL, NULL, tvp);
+	if (res <= 0)
+		return EOF;
+
+	return getchar();
+}
+
 #elif defined(GIT_WINDOWS_NATIVE)
 
 #define INPUT_PATH "CONIN$"
@@ -257,6 +282,16 @@ static int mingw_getchar(void)
 }
 #define getchar mingw_getchar
 
+static int getchar_with_timeout(int timeout)
+{
+	struct pollfd pfd = { .fd = 0, .events = POLLIN };
+
+	if (poll(&pfd, 1, timeout) < 1)
+		return EOF;
+
+	return getchar();
+}
+
 #endif
 
 #ifndef FORCE_TEXT
@@ -407,12 +442,7 @@ int read_key_without_echo(struct strbuf *buf)
 		 * half a second when we know that the sequence is complete.
 		 */
 		while (!is_known_escape_sequence(buf->buf)) {
-			struct pollfd pfd = { .fd = 0, .events = POLLIN };
-
-			if (poll(&pfd, 1, 500) < 1)
-				break;
-
-			ch = getchar();
+			ch = getchar_with_timeout(500);
 			if (ch == EOF)
 				break;
 			strbuf_addch(buf, ch);