shred: provide --remove methods to avoid excessive syncing

A sync operation is very often expensive.  For illustration
I timed the following python script which indicated that
each ext4 dir sync was taking about 2ms and 12ms, on an
SSD and traditional disk respectively.

  import os
  d=os.open(".", os.O_DIRECTORY|os.O_RDONLY)
  for i in range(1000):
     os.fdatasync(d)

So syncing for each character for each file can result
in significant delays.  Often this overhead is redundant,
as only the data is sensitive and not the file name.
Even if the names are sensitive, your file system may
employ synchronous metadata updates, which also makes
explicit syncing redundant.

* tests/misc/shred-remove.sh: Ensure all the new parameters
actually unlink the file.
* doc/coreutils.texi (shred invocation): Describe the new
parameters to the --remove option.
* src/shred.c (Usage): Likewise.
(main): Parse the new options.
(wipename): Inspect the new enum to see which of
the now optional tasks to perform.
* NEWS: Mention the new feature.
* THANKS.in: Add reporter Joseph D. Wagner

1 files changed, 1 insertions, 0 deletions

diff --git a/THANKS.in b/THANKS.in
index 891b376e0..658837601 100644
--- a/THANKS.in
+++ b/THANKS.in
@@ -316,6 +316,7 @@ Jon Peatfield                       J.S.Peatfield@damtp.cam.ac.uk
 Joost van Baal                      joostvb@xs4all.nl
 Jordi Pujol                         jordipujolp@gmail.com
 Jorge Stolfi                        stolfi@ic.unicamp.br
+Joseph D. Wagner                    joe@josephdwagner.info
 Joseph S. Myers                     jsm28@cam.ac.uk
 Josh Triplett                       josh@freedesktop.org
 Joshua Hudson                       joshudson@gmail.com