doc: clarify that du operands are interdependent

Following on from http://bugs.gnu.org/17546
make it more obvious that du may elide specified operands
to avoid double counting in the set.

* src/du.c (usage): Specify that du operates on the set of
operands, rather than each independently.
* doc/coreutils.texi (du invocation): Likewise.  Also state
that the number of entries printed may change due to the
order specified.  Currently, deeper items specified earlier
will result in them being displayed, but don't mention that
implementation detail in the documentation.
* THANKS.in: Add reporter.
Reported by Stephen Shirley

3 files changed, 4 insertions, 3 deletions

diff --git a/THANKS.in b/THANKS.in
index 3f71fef22..3451c6389 100644
--- a/THANKS.in
+++ b/THANKS.in
@@ -573,6 +573,7 @@ Stéphane Chazelas                   Stephane_CHAZELAS@yahoo.fr
 Stephen Depooter                    sbdep@myrealbox.com
 Stephen Eglen                       eglen@pcg.wustl.edu
 Stephen Gildea                      gildea@stop.mail-abuse.org
+Stehpen Shirley                     kormat@gmail.com
 Stephen Smoogen                     smooge@mindspring.com
 Steve McConnel                      steve@acadcomp.sil.org
 Steve McIntyre                      steve@einval.com
diff --git a/doc/coreutils.texi b/doc/coreutils.texi
index f6aef2dd0..1cc65329c 100644
--- a/doc/coreutils.texi
+++ b/doc/coreutils.texi
@@ -11496,7 +11496,7 @@ or @option{-x} is used together with a file name argument.
 @cindex file space usage
 @cindex disk usage for files
 
-@command{du} reports the amount of disk space used by the specified files
+@command{du} reports the amount of disk space used by the set of specified files
 and for each subdirectory (of directory arguments).  Synopsis:
 
 @example
@@ -11511,7 +11511,7 @@ Non-integer quantities are rounded up to the next higher unit.
 If two or more hard links point to the same file, only one of the hard
 links is counted.  The @var{file} argument order affects which links
 are counted, and changing the argument order may change the numbers
-that @command{du} outputs.
+and entries that @command{du} outputs.
 
 The program accepts the following options.  Also see @ref{Common options}.
 
diff --git a/src/du.c b/src/du.c
index e803e69c5..65fc0742f 100644
--- a/src/du.c
+++ b/src/du.c
@@ -283,7 +283,7 @@ Usage: %s [OPTION]... [FILE]...\n\
   or:  %s [OPTION]... --files0-from=F\n\
 "), program_name, program_name);
       fputs (_("\
-Summarize disk usage of each FILE, recursively for directories.\n\
+Summarize disk usage of the set of FILEs, recursively for directories.\n\
 "), stdout);
 
       emit_mandatory_arg_note ();