Simultaneous edits to bugs lose information

[Stuart Langridge]

If two people edit a bug simultaneously, some changes made by the first person (such as to assignee or status) will be lost when the second person submits their comment.

For example, if the sequence is like this:

1. Bug filed by Random User.
2. Project Hacker 1 views bug with a mind to assign it to himself.
3. Project Hacker 2 views bug with a mind to assign it to herself. Note that the "assigned to" and "status" fields will be unset on PH2's screen.
4. PH1 sets "assignee" to PH1 and "status" to "In Progress",and submits.
5. PH2 sets "status" to "Needs info" and leaves "assignee" unset, and submits.

The bug will have assignee and status as PH2 set them. PH1 is not assigned to this bug any more, which might puzzle him somewhat.

Exactly this happened to https://launchpad.net/distros/ubuntu/+source/jokosher/+bug/74081 if a real testcase is useful.

Fixing this will probably be massively hard, and I (PH2 in this example) noticed it when I got the emails about the bug, so perhaps that's enough.