[Toybox] [PATCH] tar: Fix support for long symbolic links

[Rob Landley]

On 3/21/19 5:08 PM, Rob Landley wrote:
> P.S. Plenty of todos that aren't in the file, those were just notes on lines of
> code as I was going past. For example, I'm adding an xabspath() constraint where
> each name it's about to create has to fit under the top level directory it's
> exracting under, that's why I'm storing the abspath of cwd in main. This
> _doesn't_ apply to symlinks but _does_ apply to hardlinks. And then there's the
> whole sparse file can of worms, and xattr/selinux support.

Speaking of which, piece of lib/args.c infrastructure plumbing I've been
pondering: there are a lot of "-no-thingy" flags that switch off "-thingy"
flags, I can add a punctuation indicator at the start of the optflag string so
any flag can be switched off by the relevant -no flag automatically.

BUT that leaves a hole where the flag defaults to on and the -no turns it _off_,
which is the case for tar's -no-same-owner when run as root. I can add another
marker for "this flag defaults on when user is root", or I could add a
TOYFLAG_DEFER_ARGS so the main() function can call get_optflags() itself (after
doing flag setup)...

Hmmm, what I should _really_ do is triage all the main() functions and see what
leftover manual processing we do with the options now, and if any of that is
amenable to genericization...

Rob