mingw: fix isatty() after dup2()

dscho · gitster · commit ff8978d53320 · 2018-10-31T12:48:59.000+09:00
Since a9b8a09 (mingw: replace isatty() hack, 2016-12-22), we handle isatty() by special-casing the stdin/stdout/stderr file descriptors, caching the return value. However, we missed the case where dup2() overrides the respective file descriptor. That poses a problem e.g. where the `show` builtin asks for a pager very early, the `setup_pager()` function sets the pager depending on the return value of `isatty()` and then redirects stdout. Subsequently, `cmd_log_init_finish()` calls `setup_pager()` *again*. What should happen now is that `isatty()` reports that stdout is *not* a TTY and consequently stdout should be left alone. Let's override dup2() to handle this appropriately. This fixes git-for-windows#1077 Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/compat/mingw.h b/compat/mingw.h
@@ -390,6 +390,9 @@ int mingw_raise(int sig);
 int winansi_isatty(int fd);
 #define isatty winansi_isatty
 
+int winansi_dup2(int oldfd, int newfd);
+#define dup2 winansi_dup2
+
 void winansi_init(void);
 HANDLE winansi_get_osfhandle(int fd);
 
diff --git a/compat/winansi.c b/compat/winansi.c
@@ -474,6 +474,18 @@ static void die_lasterr(const char *fmt, ...)
 	va_end(params);
 }
 
+#undef dup2
+int winansi_dup2(int oldfd, int newfd)
+{
+	int ret = dup2(oldfd, newfd);
+
+	if (!ret && newfd >= 0 && newfd <= 2)
+		fd_is_interactive[newfd] = oldfd < 0 || oldfd > 2 ?
+			0 : fd_is_interactive[oldfd];
+
+	return ret;
+}
+
 static HANDLE duplicate_handle(HANDLE hnd)
 {
 	HANDLE hresult, hproc = GetCurrentProcess();
