adding conditionals to jobs/tasks

[Jason]

So i have a repo with two projects and a common folder

looks like thing like:

```
|

|-Proj1

|-Common

|-Proj2

```

Proj1 and Proj2 both include Common in their project files.

I'm trying to get CI to build smart here. 

IF (files in common were changed) {
     build both projects

} ELSE {
     IF (files in Proj 1 were changed) {

          build proj 1

    } ELSE {

          build proj 2

    }

}

Something like this. Any thoughts?