tar writer: replace PAX headers with GNU extensions

Some experiments seem to indicate that the various GNU extensions are
more widely supported than their POSIX equivalents[1]. Possibly because
they are easier to implement and possibly because of the wide spread
use of GNU tar.

This commit replaces the PAX writer in the write_tar_header implementation
with a GNU extension based writer.

The writer is also cleaned up by removing all global state. The record
counter is moved outside into the tar2sqfs program and passed in as
function argument.

[1] https://dev.gentoo.org/~mgorny/articles/portability-of-tar-features.html

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

1 files changed, 5 insertions, 4 deletions

diff --git a/doc/sqfs2tar.1 b/doc/sqfs2tar.1
index a999dff..b732d06 100644
--- a/doc/sqfs2tar.1
+++ b/doc/sqfs2tar.1
@@ -18,10 +18,11 @@ Print help text and exit.
 .TP
 \fB\-\-version\fR, \fB\-V\fR
 Print version information and exit.
-.SH LIMITATIONS
-To be compatible with as many tools as possible, the output format is POSIX tar
-using pax extensions if necessary, so the tools you intend to use should
-support the pax format.
+.SH COMPATIBILITY
+To be compatible with as many tools as possible, the output format is pre-POSIX
+ustar archive using GNU extensions where necessary. This seems to be more
+widely supported by many tar programs (besides GNU tar), even more than the
+newer POSIX format and PAX extensions.
 
 It is not possible to store socket files in a tar or pax archive. Also, in the
 current implementation, all extended attribuates are lost.