UPDATE: This is old question. TFS now fully support integration with Bitbucket!
Is it really not possible to trigger build in TFS/VSTS 2015 from outside with http?
I have repository on BitBucket and I want to trigger build on commit. I have searched the web and found nothing.
Yes, unless you use a third party service like Zapier.
There is already a user voice submitted for this. check this link for details: https://visualstudio.uservoice.com/forums/330519-team-services/suggestions/10674648-enable-ci-build-support-for-bitbucket-git-reposito
Update: This feature is available in VSTS now. You can choose "BitBucket" as the "Srouce" and enable the trigger under "Triggers" panel.