In the case that you have a branch you want to merge that is giving a lot of conflicts, it's quite often that you trust all the commits in the branch to be merged and you want some kind of way to add those during the merge by default.
Here is one way to do that painlessly.
git checkout my-branch
git merge branch-you-want-to-merge
At this point, there may be a bunch of conflicts. Run the following, rememberint the dot '.' when checking out.
git checkout --theirs .