[PATCH] tar: allow creating empty archive when -T is set

[Sertonix]

This matches the GNU tar behaviour. Usefull when something needs to be
tarball but shouldn't contain any files.

function                                             old     new   delta
tar_main                                            1272    1278      +6
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/0 up/down: 6/0)                 Total: 6 bytes
---
 archival/tar.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/archival/tar.c b/archival/tar.c
index d6ca6c1e0..3983fb36e 100644
--- a/archival/tar.c
+++ b/archival/tar.c
@@ -1139,8 +1139,8 @@ int tar_main(int argc UNUSED_PARAM, char **argv)
 		int flags = O_RDONLY;
 
 		if (opt & OPT_CREATE) {
-			/* Make sure there is at least one file to tar up */
-			if (tar_handle->accept == NULL)
+			/* Make sure there is at least one file to tar up when not using -T */
+			if (tar_handle->accept == NULL && !(opt & OPT_INCLUDE_FROM))
 				bb_simple_error_msg_and_die("empty archive");
 
 			tar_fd = STDOUT_FILENO;
-- 
2.48.1