Using a diff patch is often times overlooked as a merge strategy because not many people know it exists. This is really useful when you have two branches that have diverged commit wise or if you only want to merge/revert diff from specific files but not cherry-pick the entire commit.
You want can use git diff of the exact things you want to merge/revert.
Apply branch_beta changes on file_or_file_i_actually_want_to_merge on branch_alpha
git checkout branch_alpha
git diff branch_alpha..branch_beta file_or_file_i_actually_want_to_merge > ~/merge_from_branch_beta.diff
git apply ~/merge_from_branch_beta.diff
Revert changes made on branch_beta back into the branch_alpha version
git checkout branch_beta
git diff branch_beta..branch_alpha file_or_file_i_actually_want_to_merge > ~/revert_to_branch_alpha.diff
git apply ~/revert_to_branch_alpha.diff