git branch --set-upstream-to <remote-branch>
# example
git branch --set-upstream-to origin feature-branch

# show up which remote branch a local branch is tracking
git branch -vv

sets the default remote branch for the current local branch.

Any future git pull command (with the current local branch checked-out), will attempt to bring in commits from the into the current local branch.

One way to avoid having to explicitly do --set-upstream is to use the shorthand flag -u along-with the very first git push as follows

git push -u origin local-branch