An attachment artifact associates some other artifact that is the
attachment (the source artifact) with a ticket or wiki page to which
the attachment is connected (the target artifact).
The following cards are allowed on an attachment artifact:

<blockquote>
<b>A</b> (<b>+</b>|<b>-</b>)<i>filename target source</i>
<b>A</b> <i>filename target</i> ?<i>source</i>?
<b>C</b> <i>comment</i><br>
<b>D</b> <i>time-and-date-stamp</i><br />
<b>U</b> <i>user-name</i><br />
<b>Z</b> <i>checksum</i>
</blockquote>

The A card specifies a filename for the attachment in its first argument.
The filename is preceeded by "+" to add the attachment or "-" to
remove the attachment.  The second argument to the A card is the name
The second argument to the A card is the name
of the wiki page or ticket to which the attachment is connected.  The
third argument is is the 40-character artifact ID of the attachment
itself.  Every attachment artifact must have exactly one A card.
third argument is either missing or else it is the 40-character artifact 
ID of the attachment itself.  A missing third argument means that the
attachment should be deleted.

The C card is an optional comment describing what the attachment is about.
The C card is optional, but there can only be one.

A single D card is required to give the date and time when the attachment
was applied.

<th>Cluster</th>
<th>Control</th>
<th>Wiki</th>
<th>Ticket</th>
<th>Attachment</th>
</tr>
<tr>
<td><b>A</b> (<b>+</b>|<b>-</b>)<i>filename target source</i></td>
<td><b>A</b> <i>filename target source</i></td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td align=center><b>X</b></td>
</tr>