Change default commit message when merging

When merging a pull request Bitbucket, by default, creates automated commit message like this:

Merged in CS-566 \([PR#1054|https://bitbucket.org/site/master/pull-requests/1054]\)
CS-566: General tab is not opening when Additional Liabilities - Loan is selected
…

It starts with Merged in … which is not meaningful enough. We would like to customize the default behavior so that the second line become first. In the example above, the first line of the message should be CS-566: General tab …

Thanks in advance!