How to View Commit History in Git?

The commit history in Git is like a timeline of all the changes made to a project, capturing every modification, addition, and bug fix. Accessing this history is essential for understanding project evolution, tracking down bugs, reviewing code changes, and collaborating with team members.

In this blog, we’ll explore different ways to view and analyze commit history in Git, from simple logs to more advanced filtering options.

Why View Commit History?

Viewing commit history helps with:

• Tracking Changes: Understand what changes have been made and when.
• Collaborating with Teams: See who contributed to specific changes.
• Debugging: Identify when and why a bug was introduced.
• Project Documentation: A clean commit history serves as documentation of a project’s progress.

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Basic Command to View Git Commit History

The git log command is the primary way to view commit history in Git. Running this command in your terminal or command prompt will display a list of all commits in the current branch, with details about each commit.

1. Open Terminal or Command Prompt in your Git repository.
2. Run the git log Command:

   git log

This command will output the history of commits in reverse chronological order (newest first), displaying information such as:

• Commit Hash: A unique identifier for each commit.
• Author: The person who made the commit.
• Date: When the commit was made.
• Commit Message: A description of what the commit entails.

Example Output:

commit a1b2c3d4e5f6g7h8i9j0
Author: John Doe <[email protected]>
Date:   Fri Oct 29 10:00:00 2023 -0400

    Add new feature to homepage

commit b2c3d4e5f6g7h8i9j0a1
Author: Jane Smith <[email protected]>
Date:   Thu Oct 28 15:30:00 2023 -0400

    Fix typo in README

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Customizing git log Output

Git provides several options to customize the git log output, helping you find specific information quickly.

1. One-Line Log Output

If you only need a summary of commits, the --oneline option provides a condensed view, showing each commit on a single line:

git log --oneline

Example Output:

a1b2c3d Add new feature to homepage
b2c3d4e Fix typo in README

The one-line format is especially helpful for getting an overview of recent commits.

2. Show Commit History with a Graph

To view commit history in a graphical format, use the --graph option. This is particularly useful for visualizing branch structures and merge points.

git log --oneline --graph --all

This command displays a condensed commit history with a graphical representation of branches, showing merges and diverging branches.

3. Filtering by Author

To view commits by a specific author, use the --author option followed by the author’s name or email:

git log --author="John Doe"

This filter is useful for tracking contributions by individual team members.

4. Limiting the Number of Commits Displayed

You can limit the number of commits displayed by using the -n option, where n is the number of commits:

git log -5

This command shows only the last five commits, which can be helpful when checking recent changes without needing the entire history.

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Viewing Commit History with Date Filtering

Git allows you to filter commit history by date, making it easier to locate changes within specific time frames. Here are some commonly used options:

1. Since a Specific Date:

   git log --since="2023-01-01"

This shows commits from January 1, 2023, onward.

2. Until a Specific Date:

   git log --until="2023-10-01"

This command will display commits made up to October 1, 2023.

3. Between Two Dates:

   git log --since="2023-01-01" --until="2023-10-01"

This option filters commits made between January 1 and October 1, 2023.

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Searching Commit History with Keywords

Git allows you to search commit history for specific keywords, making it easier to find relevant changes.

• Search by Commit Message: Use the --grep option to search for keywords within commit messages:

  git log --grep="bug fix"

This command will display commits with “bug fix” in the commit message.

• Search by File Name: If you want to see the history of changes to a particular file, specify the file name after git log:

  git log -- filename.txt

This command shows commits that modified filename.txt.

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Advanced Git Log Options

Git offers several advanced options for users who need more detailed insights.

1. Display Changes with Each Commit

To see the differences introduced by each commit, use the -p option:

git log -p

This shows each commit with the exact changes it introduced, which is useful for reviewing code changes in detail.

2. Display Statistics for Each Commit

The --stat option summarizes the number of insertions and deletions for each commit:

git log --stat

Example Output:

commit a1b2c3d4e5f6g7h8i9j0
Author: John Doe <[email protected]>
Date:   Fri Oct 29 10:00:00 2023 -0400

    Add new feature to homepage

 src/homepage.js | 10 ++++++++++
 1 file changed, 10 insertions(+)

The --stat output provides a summary of the affected files and lines of code, giving you a quick overview of each commit’s impact.

3. Display Only Merged Commits

To view only commits that involved a merge, use the --merges option:

git log --merges

This filter is particularly useful for tracking integration points in the project’s history.

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Practical Example: Viewing Commit History in a Workflow

Let’s go through a quick example of viewing commit history in a typical workflow.

1. Check Recent Commits:

   git log -3 --oneline

This shows the last three commits in a simplified, one-line format.

2. Identify the Author of a Recent Bug Fix:

   git log --author="Jane Smith" --grep="fix"

This command filters for commits by Jane Smith that include “fix” in the message.

3. View Detailed Changes in a Specific File:

   git log -p -- src/app.js

This command shows a line-by-line history of changes in app.js, including detailed diffs.

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Best Practices for Managing Commit History

1. Write Clear Commit Messages: Clear, descriptive commit messages make the history more readable and valuable for future reference.
2. Use Branches Effectively: Keeping feature work and bug fixes in separate branches can make your commit history more organized.
3. Rebase to Clean Up Commits: Use git rebase (for local branches) to clean up and organize commits before merging, creating a more streamlined history.

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Viewing Commit History in GitHub or GitLab

If you’re using a platform like GitHub or GitLab, viewing commit history can also be done through the web interface.

1. Navigate to the Repository: Open the repository on GitHub or GitLab.
2. Click on the Commits Tab: Most platforms have a “Commits” tab where you can view commit history for each branch.
3. Use Search and Filters: Many Git interfaces offer options to search by author, date, and commit message, similar to the git log command.

These platforms make it easy to quickly review commits and access metadata, such as pull request associations.

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Conclusion

Accessing and understanding Git commit history is crucial for effective project management, debugging, and collaboration. Whether you’re working from the command line, in a Git GUI, or on a platform like GitHub, mastering these commands will enable you to navigate your project’s history confidently. By following this guide, you can easily view, filter, and analyze commit history, ensuring you’re fully informed about the progress and changes in your codebase.