I will use these two branches in this example:

• dev - the main branch
• feature - the newly created branch

Always rebase before a merge

# checkout new branch
> git checkout -b feature

# make commits
> ...

# make a pull with rebase before merge (if long branch, do occasional rebases)
> git checkout dev
> git pull --rebase
> git checkout feature
> git rebase dev

# merge when done
> git checkout dev
> git merge feature

# delete branch
> git branch -d feature