[git] How to resolve git's "not something we can merge" error

This error suggest that the branch from where you want to merge changes (i.e. in you case branch-name) is not present in you local, so you should checkout the branch and fetch the local changes. Checkout to your master branch and fetch, then follow the below steps:

git checkout branch-name
git pull
git checkout new-branch-name
git merge branch-name