New option --sort=ORDER

This option makes tar sort the entries of directories that will be
added to an archive according to ORDER (none, name, or order).

Based on proposition by Dick Streefland (https://savannah.gnu.org/patch/?7892).

* src/common.h (savedir_sort_order): New global.
* src/create.c: Pass savedir_sort_order to streamsavedir.
* src/misc.c: Likewise.
* src/tar.c: New option --sort.

* NEWS: Update.
* doc/tar.texi: Document the --sort option.
* doc/tar.1: Likewise.

NEWS

@@ -1,4 +1,4 @@
-GNU tar NEWS - User visible changes. 2014-02-13
+GNU tar NEWS - User visible changes. 2014-02-14
 Please send GNU tar bug reports to <bug-tar@gnu.org>
 
 
@@ -35,6 +35,19 @@ supplied DIRectory.  This ensures that no archive members are
 extracted outside of the specified directory, even if the archive is
 crafted so as to put them elsewhere.
 
+* New option --sort
+
+The --sort=ORDER option instructs tar to sort directory entries
+according to ORDER.  It takes effect when creating archives.
+Available ORDERs are: none (the default), name and inode.  The
+latter may be absent, if the underlying system does not provide
+the necessary information.
+
+Using --sort=name ensures the member ordering in the created archive
+is uniform and reproducible.  Using --sort=inode reduces the number
+of disk seeks made when creating the archive and thus can considerably
+speed up archivation.
+
 * Manpages
 
 This release includes official tar(1) and rmt(8) manpages.

doc/tar.1

@@ -13,7 +13,7 @@
 .\"
 .\" You should have received a copy of the GNU General Public License
 .\" along with this program.  If not, see <http://www.gnu.org/licenses/>.
-.TH TAR 1 "January 28, 2014" "TAR" "GNU TAR Manual"
+.TH TAR 1 "February 14, 2014" "TAR" "GNU TAR Manual"
 .SH NAME
 tar \- an archiving utility
 .SH SYNOPSIS
@@ -506,6 +506,24 @@ Try extracting files with the same ownership as exists in the archive
 .TP
 \fB\-s\fR, \fB\-\-preserve\-order\fR, \fB\-\-same\-order\fR
 Sort names to extract to match archive
+.TP
+\fB\-\-sort=\fIORDER\fR
+When creating an archive, sort directory entries according to
+\fIORDER\fR, which is one of
+.BR none ,
+.BR name ", or"
+.BR inode .
+
+The default is \fB\-\-sort=none\fR, which stores archive members in
+the same order as returned by the operating system.
+
+Using \fB\-\-sort=name\fR ensures the member ordering in the created archive
+is uniform and reproducible.
+
+Using \fB\-\-sort=inode\fR reduces the number of disk seeks made when
+creating the archive and thus can considerably speed up archivation.
+This sorting order is supported only if the underlying system provides
+the necessary information.
 .SS Device selection and switching
 .TP
 \fB\-f\fR, \fB\-\-file\fR=\fIARCHIVE\fR

doc/tar.texi

@@ -3319,6 +3319,27 @@ The @option{--warning=existing-file} option can be used together with
 this option to produce warning messages about existing old files
 (@pxref{warnings}).
 
+@opsummary{sort}
+@item --sort=@var{order}
+Specify the directory sorting order when reading directories.
+@var{Order} may be one of the following:
+
+@table @samp
+@item none
+No directory sorting is performed. This is the default.
+
+@item name
+Sort the directory entries on name. The operating system may deliver
+directory entries in a more or less random order, and sorting them
+makes archive creation reproducible.
+
+@item inode
+Sort the directory entries on inode number. Sorting directories on
+inode number may reduce the amount of disk seek operations when
+creating an archive for some file systems.
+
+@end table
+
 @opsummary{sparse}
 @item --sparse
 @itemx -S

src/common.h

@@ -386,6 +386,8 @@ GLOBAL dev_t root_device;
 /* Unquote filenames */
 GLOBAL bool unquote_option;
 
+GLOBAL int savedir_sort_order;
+
 /* Show file or archive names after transformation.
    In particular, when creating archive in verbose mode, list member names
    as stored in the archive */

src/create.c

@@ -1288,7 +1288,7 @@ get_directory_entries (struct tar_stat_info *st)
   while (! (st->dirstream = fdopendir (st->fd)))
     if (! open_failure_recover (st))
       return 0;
-  return streamsavedir (st->dirstream);
+  return streamsavedir (st->dirstream, savedir_sort_order);
 }
 
 /* Dump the directory ST.  Return true if successful, false (emitting

src/misc.c

@@ -1239,7 +1239,7 @@ tar_savedir (const char *name, int must_exist)
       open_error (name);
     }
   else if (! ((dir = fdopendir (fd))
-	      && (ret = streamsavedir (dir))))
+	      && (ret = streamsavedir (dir, savedir_sort_order))))
     savedir_error (name);
 
   if (dir ? closedir (dir) != 0 : 0 <= fd && close (fd) != 0)

src/tar.c

@@ -51,6 +51,7 @@
 #include <xstrtol.h>
 #include <stdopen.h>
 #include <priv-set.h>
+#include <savedir.h>
 
 /* Local declarations.  */
 
@@ -342,6 +343,7 @@ enum
   SHOW_SNAPSHOT_FIELD_RANGES_OPTION,
   SHOW_TRANSFORMED_NAMES_OPTION,
   SKIP_OLD_FILES_OPTION,
+  SORT_OPTION,
   SPARSE_VERSION_OPTION,
   STRIP_COMPONENTS_OPTION,
   SUFFIX_OPTION,
@@ -551,6 +553,13 @@ static struct argp_option options[] = {
       " directories until the end of extraction"), GRID+1 },
   {"no-delay-directory-restore", NO_DELAY_DIRECTORY_RESTORE_OPTION, 0, 0,
    N_("cancel the effect of --delay-directory-restore option"), GRID+1 },
+  {"sort", SORT_OPTION, N_("ORDER"), 0,
+#if D_INO_IN_DIRENT
+   N_("directory sorting order: none (default), name or inode"
+#else
+   N_("directory sorting order: none (default) or name"
+#endif
+     ), GRID+1 },
 #undef GRID
 
 #define GRID 55
@@ -1310,6 +1319,21 @@ parse_owner_group (char *arg, uintmax_t field_max, char const **name_option)
 /* Either NL or NUL, as decided by the --null option.  */
 static char filename_terminator;
 
+static char const *const sort_mode_arg[] = {
+  "none",
+  "name",
+  "inode",
+  NULL
+};
+
+static int sort_mode_flag[] = {
+    SAVEDIR_SORT_NONE,
+    SAVEDIR_SORT_NAME,
+    SAVEDIR_SORT_INODE
+};
+
+ARGMATCH_VERIFY (sort_mode_arg, sort_mode_flag);
+
 static error_t
 parse_opt (int key, char *arg, struct argp_state *state)
 {
@@ -1997,6 +2021,11 @@ parse_opt (int key, char *arg, struct argp_state *state)
       show_transformed_names_option = true;
       break;
 
+    case SORT_OPTION:
+      savedir_sort_order = XARGMATCH ("--sort", arg,
+				      sort_mode_arg, sort_mode_flag);
+      break;
+
     case SUFFIX_OPTION:
       backup_option = true;
       args->backup_suffix_string = arg;
@@ -2274,6 +2303,8 @@ decode_options (int argc, char **argv)
   tar_sparse_major = 1;
   tar_sparse_minor = 0;
 
+  savedir_sort_order = SAVEDIR_SORT_NONE;
+  
   owner_option = -1; owner_name_option = NULL;
   group_option = -1; group_name_option = NULL;