rsync - Apr 2007 - Modifications to NOT recursively make_backup

Hi:

	Suppose I have the following files on my target volume:

/Applications/[45,000 sub files and directories]
/Developer/[120,000 sub files and directories]
... (another 8 or so directories with lots of files and sub directories)
/usr/ [75,000 sub files and directories]

For a total of approximately 500K files and directories.  On my  
source, I have only a handful of items:

/Data/ [70 items]
/Records/ [20 items]
/Finances/ [45 items]

Now I want to copy source to target, while archiving what is already  
on the target:

rsync -a --backup --backup-dir="backup_2007_04_03_14-03-34" --delete /
Volumes/Source/ /Volumes/Target

The result is that it takes an incredibly long time to move  
essentially everything on the target -- one at a time -- to the  
backup directory on the target.  Instead of recognizing that each of  
the 11 root items on the target do not exist on the source, rsync  
does a depth-first backup and thus performs 500K mv operations.

My questions is why?  I made the following modifications to  
generator.c and backup.c (2.6.6) which eliminates the depth-first  
backup and immediately backs up the root items, but I'm wondering if  
there was a specific reason to do a depth-first backup instead, and  
if my changes will have an adverse or unexpected result.  In my  
testing, it appears to be OK, but the code I'm replacing looks very  
deliberate.

Thanks,
Mike


*** rsync 2.6.6/generator.c Mon Mar 12 21:04:28 2007
--- rsync 2.6.6+/generator.c   Mon Apr  2 19:21:09 2007
*************** static int delete_item(char *fname, int
*** 190,197 ****
             || (dry_run && zap_dir)) {
                 ok = 0;
                 errno = ENOTEMPTY;
!      } else if (make_backups && !backup_dir &&
!is_backup_file(fname)
-           && !(flags & DEL_FORCE_RECURSE))
                 ok = make_backup(fname);
         else
                 ok = do_rmdir(fname) == 0;
--- 190,198 ----
             || (dry_run && zap_dir)) {
                 ok = 0;
                 errno = ENOTEMPTY;
!       } else if (make_backups)
                 ok = make_backup(fname);
         else
                 ok = do_rmdir(fname) == 0;


*** rsync 2.6.6/backup.c    Sun Mar 25 20:57:48 2007
--- rsync 2.6.6+/backup.c      Tue Apr  3 13:15:32 2007
*************** static int keep_backup(char *fname)
*** 204,222 ****
         }

         if (!kept && S_ISDIR(file->mode)) {
!               /* make an empty directory */
!               if (do_mkdir(buf, file->mode) < 0
!                   && (errno != ENOENT || make_bak_dir(buf) < 0
!                    || do_mkdir(buf, file->mode) < 0)) {
!                       rsyserr(FINFO, errno, "mkdir %s failed",
!                               full_fname(buf));
                 }

-               ret_code = do_rmdir(fname);
-               if (verbose > 2) {
-                       rprintf(FINFO, "make_backup: RMDIR %s returns  
%i\n",
-                               full_fname(fname), ret_code);
-               }
                 kept = 1;
         }

--- 204,214 ----
         }

         if (!kept && S_ISDIR(file->mode)) {
!               if (robust_move(fname, buf) != 0) {
!                       rsyserr(FERROR, errno, "keep_backup failed: % 
s -> \"%s\"",
!                               full_fname(fname), safe_fname(buf));
                 }

                 kept = 1;
         }