Using the bitbucket the branch selected is not used to commit the update, the changes are applied on the master branch into a folder with the same name of the selected branch before.
Looking over the Bitbucket connector code now and.......yep it's a mess. Sorry about that, will spend some time making it better.
This should be fixed in the next release (0.2.20.Final aka Beta 2.20). Thanks for the bug report!