tar: fix too eager autodetection, closes 11531

function                                             old     new   delta
is_suffixed_with                                       -      54     +54
tar_main                                            1006    1026     +20
open_transformer                                      92      79     -13
config_file_action                                   478     458     -20
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 1/2 up/down: 74/-33)             Total: 41 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/archival/tar.c b/archival/tar.c
index 1c71f7f66..6950c271d 100644
--- a/archival/tar.c
+++ b/archival/tar.c
@@ -1162,8 +1162,16 @@ int tar_main(int argc UNUSED_PARAM, char **argv)
                         tar_handle->seek = seek_by_read;
                 } else
                 if (ENABLE_FEATURE_TAR_AUTODETECT
+                 && ENABLE_FEATURE_SEAMLESS_LZMA
                  && flags == O_RDONLY
                  && !(opt & OPT_ANY_COMPRESS)
+                 && is_suffixed_with(tar_filename, ".lzma")
+                /* We do this only for .lzma files, they have no signature.
+                 * All other compression formats are recognized in
+                 * get_header_tar() when first tar block has invalid format.
+                 * Doing it here for all filenames would falsely trigger
+                 * on e.g. tarball with 1st file named "BZh5".
+                 */
                 ) {
                         tar_handle->src_fd = open_zipped(tar_filename, /*fail_if_not_compressed:*/ 0);
                         if (tar_handle->src_fd < 0)