Comments with negative IDs on rust-lang/rust

[apiraino]

RFCbot started linking comments with a negative ID since we overflowed an i32 amount of comments in the rust-lang/rust repository.

Example: In this comment another comment was linked but the ID of the linked comment is wrong. Instead of being #issuecomment-2250077004 it's a negative comment ID (#issuecomment--2044890292) .

The GH documentation suggests storing these ID as i64 (comment on Zulip) but we store them as i32 (code, IIUC the rfcbot DB).

I wonder if it would make sense attempting to migrate these IDs to i64.

Relevant discussions on Zulip: here, here and here.

Relevant patches: 4616cbd and 20ee406 and f9d84fa