Before the upgrade to the newer, sexier BitBucket, when creating a pull request it would select sensible defaults. For example, let's say we have:
MainRepo, with 2 branches: default, stage
then I fork MainRepo as MyMainFork.
I make changes in the default branch of MyMainFork, and push them to my fork on BitBucket.
At that point, I select "Pull Request" to issue one. In the old BitBucket, by default it selected the branch w/ changesets that were ahead of the common ancestor between MainRepo and MyMainFork, and it would choose the destination repository as MainRepo.
In the new BitBucket, it picks the default branch and MyMainFork as the defaults for the Pull Request destination. This doesn't make any sense!! Why would I issue a Pull Request from MyMainFork to MyMainFork?
I've done this by accident twice now, and was left wondering why nobody could see my Pull Request.