error: Your local changes to the following files would be overwritten by checkout

I encountered the same problem and solved it by

git checkout -f branch

and its specification is rather clear.

-f, --force

When switching branches, proceed even if the index or the working tree differs from HEAD. This is used to throw away local changes.

When checking out paths from the index, do not fail upon unmerged entries; instead, unmerged entries are ignored.

Your error appears when you have modified a file and the branch that you are switching to has changes for this file too (from latest merge point).

Your options, as I see it, are - commit, and then amend this commit with extra changes (you can modify commits in git, as long as they're not pushed); or - use stash:

git stash save your-file-name
git checkout master
# do whatever you had to do with master
git checkout staging
git stash pop

git stash save will create stash that contains your changes, but it isn't associated with any commit or even branch. git stash pop will apply latest stash entry to your current branch, restoring saved changes and removing it from stash.

You can force checkout your branch, if you do not want to commit your local changes.

git checkout -f branch_name