In preparation for applying the patch series proposed in
https://inbox.sourceware.org/cygwin-patches/20230712120804.2992142-1-corinna-cygwin@cygwin.com/
let's drop this patch of ours.

Both changes are intended to fix the problem where `tar xf` would
stumble over symlinks, seemingly having trouble changing the mode bits,
but our patch addressed really only that bug while the upstream patch
series addresses the broader AT_EMPTY_PATH handling.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

The check if the local variable p is NULL is useless.  The preceeding
code always sets p to a valid pointer, or it crashes if path_ret is
invalid (which would be a bug in Cygwin).

Fixes:c57b57e5c43a ("* cygwin.din: Sort.")
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Cygwin needs an internal flag to allow specifying an empty pathname
in utimesat (GLIBC extension). We define it in _default_fcntl.h to
make sure we never introduce a value collision accidentally.
While at it, define the values as 16 bit hex values.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Convert gen_full_path_at to take flag values from the caller, rather
than just a bool indicating that empty paths are allowed.  This is in
preparation of a better AT_EMPTY_PATH handling in a followup patch.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

The GLIBC extension AT_EMPTY_PATH allows the functions fchownat
and fstatat to operate on dirfd alone, if the given pathname is an
empty string.  This also allows to operate on any file type, not
only directories.

Commit fa84aa4 broke this.  It only allows dirfd to be a
directory in calls to these two functions.

Fix that by handling AT_EMPTY_PATH right in gen_full_path_at.
A valid dirfd and an empty pathname is now a valid combination
and, noticably, this returns a valid path in path_ret.  That
in turn allows to remove the additional path generation code
from the callers.

Fixes: fa84aa4 ("Cygwin: fix errno values set by readlinkat")
Reported-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>