What is the purpose of using the base commit when performing a rebase operation?

When performing a git rebase operation, the base commit is the commit relative to which you want to rewrite your branch's history. The purpose of using a base commit is to specify the starting point for transferring changes.

For example, if you have a feature branch created from master at a certain commit, and master has moved forward, during rebase you take the base commit — the last common commit with master — and "transfer" your commits on top of the current state of master.

This allows:

• Making the commit history more linear and clean.
• Updating your branch with the latest changes from the base branch.

Example:

# Suppose you are on the feature branch
git rebase master

Here, master is the base commit (or more precisely, the branch you are rebasing onto), and your commits will be applied on top of the current master.