Best practice for when build plans need to be different per branch?

[Paul Wagland]

I was hoping to be able to use the `bamboo-specs` to define our plan per branch. This would allow us to have a different plan for each branch, and support branch, which makes sense as your build system and requirements evolves over time. So what is needed today might be different than what you needed six months ago which is where your support branch is. However the `bamboo-specs` is repository wide, and so every branch is built in an identical fashion.

What we have decided to do is to have a very simple build plan, that simply calls a script in our repository, and this script can evolve over time. However this is suboptimal, as it means that we cannot use different jobs to run different parts of the build in parallel.

Are there other approaches that can be taken? And what are the advantages/disadvantages of these?