I got two build definition that is mapped to some common folders. When I do check in it prompts me the selection box to pick up either of the build definition.
It gives me the option. Can I change my build definition to select the default based on what is triggered and show it as the first option without need for user to select the right one?
If you have two build definitions configured for the same source control folder then you will always get a choice. There is no way to set a default.
It is recommended to have only one gated-checkin configured to avoid confusion.