[PATCH 0/5] git-tar-tree: add symlink support

Since symlinks can be stored inside GIT, git-tar-tree should properly
handle them, too.  The first three patches do a bit of cleanup to make
adding symlink support easier.  The fourth patch actually dirties the
code, also to make the fifth one easier. :)  I just couldn't think of a
better way to split the changes and a combined patch of 4&5 did too much
at once.

If a link target is longer than 100 chars than an extended header is
created.  Because of the way git-tar-tree handles extended headers that
means the sum of path and target of a symlink must be less than about
490 chars.  This is not a limitation of the archive format, so we can
fix it later.

Rene