How to Check If a Git Branch Is Stale

Introduction

In this lab, you will learn how to check if a Git branch is stale by examining the date of its last commit. You will start by using the fundamental git log command to view commit history and identify the last commit date on a branch.

Next, you will explore the more powerful git for-each-ref command to efficiently retrieve the last commit date for multiple branches. Finally, you will learn how to compare the activity of different branches to determine which ones might be considered stale.

Skills Graph

Check Last Commit Date with git log

In this step, we'll use the git log command to check the date of the last commit in our repository. This is a fundamental skill for understanding the history of your project.

First, make sure you are in your my-time-machine directory. If you are not, use the cd command to navigate there:

cd ~/project/my-time-machine

Now, let's use git log to see the commit history. We'll add an option to make the output more concise and show only one line per commit, which is very useful when you have many commits.

git log --oneline

You should see output similar to this:

a1b2c3d (HEAD -> master) Send a message to the future

This output shows the abbreviated commit hash (a1b2c3d), the branch it's on (HEAD -> master), and the commit message.

To see more details, including the date and time of the commit, you can use the git log command without any options:

git log

The output will be similar to what you saw in the previous lab, showing the full commit details:

commit a1b2c3d4e5f6g7h8i9j0k1l2m3n4o5p6q7r8s9 (HEAD -> master)
Author: Jane Doe <[email protected]>
Date:   Mon Aug 7 10:00:00 2023 +0000

    Send a message to the future

The Date line shows when the commit was made. This is crucial for tracking the progress of your project and understanding the timeline of changes.

Understanding git log is essential for navigating your project's history. It allows you to see when changes were made, who made them, and what the changes were about (based on the commit message). As your project grows, this log becomes an invaluable tool for debugging, collaboration, and understanding the evolution of your code.

Use git for-each-ref for Branch Activity

In this step, we will explore a more advanced Git command, git for-each-ref, to get detailed information about our branches, including the date of the last commit on each branch. This command is very powerful for scripting and customizing Git output.

Ensure you are still in the ~/project/my-time-machine directory.

The git for-each-ref command allows you to iterate over all references (like branches and tags) in your repository and display information about them in a specified format.

Let's use it to list our branches and the date of their last commit. We'll specify the format to show the committer date and the branch name.

git for-each-ref --sort=-committerdate refs/heads/ --format='%(committerdate:short) %(refname:short)'

Let's break down this command:

• git for-each-ref: The command itself.
• --sort=-committerdate: This sorts the output by the committer date in descending order (newest first). The hyphen - before committerdate indicates descending order.
• refs/heads/: This tells Git to only look at references under refs/heads/, which are our local branches.
• --format='%(committerdate:short) %(refname:short)': This specifies the output format.
  • %(committerdate:short): Displays the committer date in a short format (YYYY-MM-DD).
  • %(refname:short): Displays the short name of the reference (the branch name).

You should see output similar to this:

YYYY-MM-DD master

The date shown is the date of the last commit on the master branch, which is the commit we created in the previous lab.

While git log is great for viewing the history of a single branch or a few commits, git for-each-ref is useful when you want to get specific information about multiple references in a structured way. This is particularly helpful in larger projects with many branches.

Understanding how to use git for-each-ref with different format options opens up many possibilities for scripting and automating tasks related to your Git repository.

Compare with Active Branches

In this step, we will compare the information we got from git log and git for-each-ref and understand how they relate to the concept of "active" branches.

Ensure you are still in the ~/project/my-time-machine directory.

We've seen that git log shows the history of the current branch by default, and git for-each-ref refs/heads/ shows information about all local branches. In our current simple repository, we only have one branch, master, so the last commit date shown by both commands will be the same.

Let's re-run the git for-each-ref command to see the output again:

git for-each-ref --sort=-committerdate refs/heads/ --format='%(committerdate:short) %(refname:short)'

Output:

YYYY-MM-DD master

And the git log --oneline command:

git log --oneline

Output:

a1b2c3d (HEAD -> master) Send a message to the future

Both commands confirm that the last activity (the last commit) in our repository is on the master branch, and they show the date of that commit.

In a real-world project with multiple branches, git for-each-ref refs/heads/ sorted by committer date is a quick way to see which branches have had recent activity. The branches at the top of the list are the ones that have been worked on most recently.

Comparing this output with the output of git log on specific branches helps you understand the overall activity in the repository and the specific history of individual branches.

For example, if you had another branch called feature-x, you could run git log feature-x --oneline to see its specific history and compare its last commit date with the date shown by git for-each-ref.

This ability to quickly see recent activity across all branches is very helpful for project managers and team leads to get an overview of development progress.

Summary

In this lab, we learned how to check if a Git branch is stale by examining its activity. We started by using the fundamental git log command to view commit history and specifically identify the date of the last commit on a branch. This provided a basic understanding of recent activity.

We then moved on to the more powerful git for-each-ref command, which allows us to retrieve detailed information about all branches, including the date of their last commit. This command is particularly useful for systematically assessing the activity across multiple branches and identifying those that haven't been updated recently.