$self->digest( "/tmp/readers" ) ;
    

Returns the Base64 MD5 digest of the named file. Used to compare a base rev (which is the revision *before* the first one we want to transfer) of a file from the source repo to the existing head rev of a dest repo.

The Base64 version is returned because that's what RevML uses and we might want to cross-check with a .revml file when debugging.

   $self->compare_base_revs( $rev, $work_path ) ;
    

Checks out the indicated revision from the destination repository and compares it (using digest()) to the file from the source repository (as indicated by $work_path). Dies with an error message if the base revisions do not match.

Calls $self->checkout_file( $rev ), which the subclass must implement.

   $dest->backfill( $rev ) ;
    

Checks the file indicated by VCP::Rev $rev out of the target repository if this destination supports backfilling. Currently, only the revml and the reporting & debugging destinations do not support backfilling.

The $rev->workpath must be set to the filename the backfill was put in.

This is used when doing an incremental update, where the first revision of a file in the update is encoded as a delta from the prior version. A digest of the prior version is sent along before the first version delta to verify it's presence in the database.

So, the source calls backfill(), which returns TRUE on success, FALSE if the destination doesn't support backfilling, and dies if there's an error in procuring the right revision.

If FALSE is returned, then the revisions will be sent through with no working path, but will have a delta record.

MUST BE OVERRIDDEN.

    sub sort_filter {
       my $self = shift;
       my @sort_keys = @_;
       return () if @sort_keys && $sort_keys[0] eq "change_id";
       require VCP::Filter::changesets;
       return ( VCP::Filter::changesets->new(), );
    }
    

This is passed a sort specification string and returns any filters needed to presort data for this destination. It may return the empty list (the default), or one or more instantiated filters.

   sub sort_filters { shift->require_change_id_sort( @_ ) }
    

   $dest->handle_footer( $footer ) ;
    

Does any cleanup necessary. Not required. Don't call this from the override.

   $dest->handle_header( $header ) ;
    

Stows $header in $self->header. This should only rarely be overridden, since the first call to handle_rev() should output any header info.

   $dest->rev_count( $number_of_revs_forthcoming );
    

Sent by the last aggregating plugin in the filter chain just before the first revision is sent to inform us of the number of revs to expect.

   $dest->handle_rev( $rev ) ;
    

Outputs the item referred to by VCP::Rev $rev. If this is the first call, then $self->none_seen will be TRUE and any preamble should be emitted.

MUST BE OVERRIDDEN. Don't call this from the override.

   my $rev_id = $dest->last_rev_in_filebranch(
      $source_repo_id,
      $source_filebranch_id
   );
    

Returns the last revision for the file and branch indicated by $source_filebranch_id. This is used to support --continue.

Returns undef if not found.