Support for 'path=', 'uname=', 'gname=', 'size=', and 'atime=' pax
headers is useful. Others are ignored, possibly with a warning.
We were running into missing support with the 'go' extraction.
At the same time, this cleans up the way that we handle paths,
getting rid of static buffers with hidden space at the front.
Tar specifies that a filename ending with '/' is a directory. We were
incorrectly looking at the short name. This meant that when we have long
filenames with a '/' at the 100th character, we would decide it was a
directory.
This change uses the long name when deciding the size for extraction,
and trusts the header size when just skipping forward in the stream.
extract1() expects two extra bytes to be avilabe before
fname buffer so it can prepend ./ before the name. this
used to be the case with name(), but was violated when
long name support was added and getname() was used in
place of name() which did not reserve the 2 extra bytes.
this change reserves two extra bytes in the getname()'s
static buffer and also removes the extra copy as name()
already makes a copy.
tar used to infer compression type from the filenames extension, but when
no file name is given (stdin/stdout), the -z flag was ignored and no
compression filter applied. this changes tar to assume the default
gzip compression method when z is given and no file name is specified.
this allows extracting tar archives that use longnames extension,
where the real filename is stored in a special entry with
linkflag == 'L' before the file entry. also skip longlink entries
with linkflag == 'K'.
