Branching from Tags in Git
Tags in Git are used to mark specific points in your repository’s history – typically releases. While tags themselves are static, you often need to create a new branch from a tag to begin work on a bug fix, hotfix, or new feature based on that release. This tutorial explains how to accomplish this effectively.
Understanding the Concept
Creating a branch from a tag doesn’t alter the tag itself. The tag continues to point to the specific commit it originally marked. Instead, a new branch is created, starting its history from that same commit. This allows you to diverge from the tagged release and make changes without affecting the integrity of the tag.
Creating a Branch from a Tag
The most common and straightforward method to create a new branch from a tag is using the git checkout command with the -b flag. The -b flag tells Git to create a new branch and switch to it.
git checkout -b <new_branch_name> <tag_name>
Replace <new_branch_name> with the desired name for your new branch and <tag_name> with the name of the tag you want to branch from.
Example:
To create a new branch named hotfix/v1.0 from the tag v1.0, you would use the following command:
git checkout -b hotfix/v1.0 v1.0
This command does two things:
- It creates a new branch named
hotfix/v1.0. - It switches your working directory to the
hotfix/v1.0branch, with its history starting at the commit pointed to by thev1.0tag.
Handling Ambiguous Tag Names
In some cases, Git might interpret the tag name as a branch name if a branch with the same name exists. If you encounter an error message like "ambiguous object name," you can explicitly specify that you’re referencing a tag by prefixing the tag name with tags/:
git checkout -b <new_branch_name> tags/<tag_name>
Example:
git checkout -b hotfix/v1.0 tags/v1.0
Creating a Branch Without Switching
If you want to create the branch without immediately switching to it, you can use the git branch command:
git branch <new_branch_name> <tag_name>
Example:
git branch hotfix/v1.0 v1.0
This command creates the hotfix/v1.0 branch, but your working directory remains on the currently checked-out branch. You can then switch to the new branch later using git checkout hotfix/v1.0.
A Modern Alternative: git switch
Git has introduced git switch and git restore as more user-friendly alternatives to git checkout. To create and switch to a new branch from a tag using git switch:
git switch -c <new_branch_name> <tag_name>
The -c flag is equivalent to -b in git checkout – it creates a new branch and switches to it.
Example:
git switch -c hotfix/v1.0 v1.0
Pushing the New Branch to a Remote Repository
Once you’ve created your branch and made changes, you’ll likely want to share it with others by pushing it to a remote repository. Use the following command:
git push -u origin <new_branch_name>
The -u flag (short for --set-upstream) establishes a tracking connection between your local branch and the remote branch, allowing you to use commands like git pull and git push more easily in the future.