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Tools → Git and GitHub →

T6L1. Creating Branches


To work in parallel timelines, you can use Git branches.

This lesson covers that part.

Git branches let you develop multiple versions of your work in parallel — effectively creating diverged timelines of your repository’s history. For example, one team member can create a new branch to experiment with a change, while the rest of the team continues working on another branch. Branches can have meaningful names, such as master, release, or draft.

A Git branch is simply a ref (a named label) that points to a commit and automatically moves forward as you add new commits to that branch. As you’ve seen before, the HEAD ref indicates which branch you’re currently working on, by pointing to corresponding branch ref.
When you add a commit, it goes into the branch you are currently on, and the branch ref (together with the HEAD ref) moves to the new commit.

Git creates a branch named master by default (Git can be configured to use a different name e.g., main).

Given below is an illustration of how branch refs move as branches evolve. Refer to the text below it for explanations of each stage.

  • There is only one branch (i.e., master) and there is only one commit on it. The HEAD ref is pointing to the master branch (as we are currently on that branch).
  • A new commit has been added. The master and the HEAD refs have moved to the new commit.
  • A new branch fix1 has been added. The repo has switched to the new branch too (hence, the HEAD ref is attached to the fix1 branch).
  • A new commit (c) has been added. The current branch ref fix1 moves to the new commit, together with the HEAD ref.
  • The repo has switched back to the master branch. Hence, the HEAD has moved back to master branch's .
    At this point, the repo's working directory reflects the code at commit b (not c).
  • A new commit (d) has been added. The master and the HEAD refs have moved to that commit.
  • The repo has switched back to the fix1 branch and added a new commit (e) to it.

Note that appearance of the revision graph (colors, positioning, orientation etc.) varies based on the Git client you use, and might not match the exact diagrams given above.

HANDS-ON: Work on parallel branches

1 Fork the samplerepo-things repo, and clone it onto your computer.

2 Observe that you are in the branch called master.

CLI
$ git status
⤷
on branch master
Sourcetree

3 Start a branch named feature1 and switch to the new branch.

CLI

You can use the branch command to create a new branch and the checkout command to switch to a specific branch.

$ git branch feature1
$ git checkout feature1

One-step shortcut to create a branch and switch to it at the same time:

$ git checkout –b feature1

The new switch command

Git recently introduced a switch command that you can use instead of the checkout command given above.

To create a new branch and switch to it:

$ git branch feature1
$ git switch feature1

One-step shortcut (by using -c or --create switch):

$ git switch –c feature1
Sourcetree

Click on the Branch button on the main menu. In the next dialog, enter the branch name and click Create Branch.

Note how the feature1 is indicated as the current branch (reason: Sourcetree automatically switches to the new branch when you create a new branch, if the Checkout New Branch was selected in the previous dialog).

4 Create some commits in the new branch. Just commit as per normal. Commits you add while on a certain branch will become part of that branch.
Note how the master ref and the HEAD ref moves to the new commit.

CLI

As before, you can use the git log --one-line --decorate command for this.

Sourcetree

  • At times, the HEAD ref of the local repo is represented as in Sourcetree, as illustrated in the screenshot below .

  • The HEAD ref is not shown in the UI if it is already pointing at the active branch.

5 Switch to the master branch. Note how the changes you did in the feature1 branch are no longer in the working directory.

CLI
$ git switch master
Sourcetree

Double-click the master branch.

Revisiting master vs origin/master

In the screenshot above, you see a master ref and a origin/master ref for the same commit. The former identifies the of the local master branch while the latter identifies the tip of the master branch at the remote repo named origin. The fact that both refs point to the same commit means the local master branch and its remote counterpart are with each other. Similarly, origin/HEAD ref appearing against the same commit indicates that of the remote repo is pointing to this commit as well.

6 Add a commit to the master branch. Let’s imagine it’s a bug fix.
To keep things simple for the time being, this commit should not involve the same content that you changed in the feature1 branch. To be on the safe side, you can change an entirely different file in this commit.

gitGraph BT:
    %%{init: { 'theme': 'default', 'gitGraph': {'mainBranchName': 'master'}} }%%
    commit id: "m1"
    commit id: "m2"
    branch feature1
    commit id: "f1"
    commit id: "[feature] f2"
    checkout master
    commit id: "[HEAD → master] m3"
    checkout feature1

7 Switch between the two branches and see how the working directory changes accordingly. That is, now you have two parallel timelines that you can freely switch between.

done!

You can also start a branch from an earlier commit, instead of the latest commit in the current branch. For that, simply check out the commit you wish to start from.

HANDS-ON: Start a branch from an earlier commit

In the samplerepo-things repo that you used above, let's create a new branch that starts from the same commit the feature1 branch started from. Let's pretend this branch will contain an alternative version of the content we added in the feature1 branch.

gitGraph BT:
    %%{init: { 'theme': 'default', 'gitGraph': {'mainBranchName': 'master'}} }%%
    commit id: "m1"
    commit id: "m2"
    branch feature1
    branch feature1-alt
    checkout feature1
    commit id: "f1"
    commit id: "[feature1] f2"
    checkout master
    commit id: "[HEAD → master] m3"
    checkout feature1-alt
    commit id: "[HEAD → feature1-alt] a1"

Avoid this rookie mistake!

Always remember to switch back to the master branch before creating a new branch. If not, your new branch will be created on top of the current branch.

  1. Switch to the master branch.
  2. Checkout the commit that is at which the feature1 branch diverged from the master branch (e.g. git checkout HEAD~1). This will create a detached HEAD.
  3. Create a new branch called feature1-alt. The HEAD will now point to this new branch (i.e., no longer 'detached').
  4. Add a commit on the new branch.

done!