opened repository db.

   If the callback returns any code other than 0 or FSL_RC_BREAK,
   looping over the list of files ends and this function returns
   that value. FSL_RC_BREAK causes looping to stop but 0 is
   returned.

   Files deleted by the given version are not reported to the callback
   (because getting sane semantics has proven to be tricker and more
   costly than it's worth). The callback is gauranteed that the order
   of the calls made to it will match the lexical ordering of the
   F-cards' names.

   See fsl_repo_extract_f() for more details about the semantics of
   the callback.

   Fossil's internal format guarantees that files will passed be
   passed to the callback in "lexical order" (as defined by fossil's
   manifest format definition). i.e. the files will be passed in

          content->used = 0;
          rc = fsl_content_get(f, fid, content);
        }
      }
      if(!rc){
        /** Call the callback. */
        xst.fc = fc;
        assert(fid>0);
        xst.content = content;
        xst.fileRid = fid;
        rc = callback( &xst );
        if(FSL_RC_BREAK==rc){
          rc = 0;
          break;
        }
      }