Let's say I have a repo that looks like this:
Repo
--a.txt
--b.txt
Let's say I create a feature branch named featureA for user A to implement a feature. After implementing feature branch would be merged back to master.
Now I want User A to work only with b.txt to implement the feature and not change a.txt but as far as I have seen user can change a.txt. So how do I restrict the user from changing a.txt? Also, I want a.txt to be in user's copy but I don't want the user to change it. Can this be done in Git or SourceTree?