Script Runner - Based on Branch Name PR's , Want to add mandatory reviewers

[User Three]

Hello, 

Just wanted to know, in my current repository i wanted to have list of auto approvers based on branch name. Context is 

Branchname1 : user1 , user2 

Branchname2: user3 , user4

Branchname3: user5, user6

Can you please help me out, when a PR is requested on branchname1 it should allow me to pick up automatically user1 and user2 as mandatory approvers.

Similarly for branchname2, when PR is requested in that branch it should autoamtically assign user3, user4.  Any idea ?