Applying the changes from branch b to a, without merging or adding commits

Question

My scenario is that I have one branch in which I\'ve made big improvements to the build process (branch A) and in another I\'m working on a unrelated feature (branch B). So

Answer 1

I'm not 100% sure I understood it clearly, but in my case I've just created diff patch between branches and then applied this path on B branch.

Inside branch A:

 git diff branchA..branchB > patch.diff
 git apply patch.diff