Download the CHAT.FILE attachment associated with a single chat entry. The "name" query parameter begins with an integer that identifies the particular chat message. The integer may be followed by a / and a filename, which will (A) indicate to the browser to use the indicated name when saving the file and (B) be used to guess the mimetype in some particular cases involving the "render" flag.

If the "render" URL parameter is provided, the blob has a size greater than zero, and blob meets one of the following conditions then the fossil-rendered form of that content is returned, rather than the original:

- Mimetype is text/x-markdown or text/markdown: emit HTML.

- Mimetype is text/x-fossil-wiki or P("name") ends with ".wiki": emit HTML.

- Mimetype is text/x-pikchr or P("name") ends with ".pikchr": emit image/svg+xml if rendering succeeds or text/html if rendering fails.