Branches

So far, all of our version histories have been sequential. Each commit follows the next in an ordered line. For example:

A single black line extends across the frame. Several points are marked; each point is a commit.

However, sometimes it can be useful to manage different versions of code simultaneously. For example, you may have a script that performs a scientific analysis, but want to use different parameters or settings for different ongoing projects. Alternatively, you may want to have a version where you can test out new features while maintaining a version you know already works. In this case, our version history might look something like this:

After the second commit, the line branches into three lines. The middle line is still black and has a commit labeled 'Set parameters'. The top line is blue and has a commit labeled 'Set different parameters'. The bottom line is red and has two commits. The first is labeled 'Start new feature' and the second is labeled 'Debugging'.

In git parlance, these concurrent versions are known as branches. Branches are derived from a common point in a version history, but each branch will have a unique history after the split point. For example, this is the version history for the default branch:

The history includes the first two commits and the 'Set parameters' commit.

whereas this is the version history for the branch implementing a new feature:

The history includes the first two commits, the 'Start new feature' commit, and the 'Debugging' commit.

You can then switch between different branches and add new commits as your needs dictate.

New Vocabulary

In the next exercise, we will see how to create and commit to different branches.

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