Fix generated commit messages with "squash" strategy enabled, currently they're useless.

We recently upgraded Bitbucket Enterprise to a version with Merge strategies per project and enabled "squash" strategy.

It works, but with major problem: resulting commit message is simply useless if you try to view project history.

Pattern is "Merge pull request #number in Project/repository from source branch to target branch \nusefulinfo"

It simply does not make sense, you always have to read full commit message body to understand what is this commit about.

Please take a look at Github implementation, they use Pull Request title as first line in commit message and then put messages from individual commits. That actually make much more sense.

In the attachment you can find history of our project once we enabled "squash" strategy, it's useless.