add attachment conversion support

[Habbie]

Hello,

this patch adds support for converting attachments. It posts them as gists (one gist per attachment) and then posts comments to the ticket.

Limitations:

• it fetches attachments over HTTP (I don't recall whether they're in the trac DB too)
• the comments linking to the attachments appear before all other comments, instead of chronologically like in Trac

When I used this, I hardcoded the URL. For this pull request, I moved the URL to a variable. I did not test this.

I extracted this patch from a bigger bunch of changes; I did not test the code after extraction. If anything is broken, my apologies.

[Habbie]

Replying to #5 I realise this pull request depends on SQLite. Remove rowid, from the query, and from one of the prints, and it is portable to MySQL.

[trustmaster]

Does it have to have both $row['id'] and $row['rowid'] for SQLite?

[ctrueden]

@trustmaster: I am no expert, but at least with my SQLite3 Trac environments, here's what I see:

sqlite> select count(*) from `ticket`;
822
sqlite> select count(*) from `ticket` where rowid <> id;
0

I am guessing id vs. rowid doesn't matter unless you start manually deleting rows from your ticket table.

So for consistency (assuming @Habbie ever comes back to this), I would suggest the patch just use $row['id'] like everywhere else does.

[Habbie]

id vs. rowid actually makes a big difference in the attachment table:

sqlite> select id,rowid from attachment limit 3;
8|1
8|2
8|3

However, the only reason rowid is in the select is so we can print it. Drop it from the select, drop the print, everything should work with both SQLite and MySQL again.