{"title":"Viewing Commit History (git log)","description":null,"content":"Understanding the history of your project is crucial when working with Git.\n\nThe `git log` command serves as your time machine, allowing you to see a detailed history of all your commits. It is not just a list of changes; it provides context, authorship, dates, and much more. \n\nIn this chapter we will learn what `git log` is and how to leverage it effectively to enhance your workflow significantly.\n\n---\n\n# The Basics of `git log`\n\nAt its core, `git log` displays the commit history of your repository. When you run this command, Git traverses the commit graph and presents a chronological list of commits.\n\nEach entry contains vital information, including:\n\n- **Commit Hash**: A unique identifier for the commit.\n- **Author**: The person who made the changes.\n- **Date**: When the commit was created.\n- **Commit Message**: A brief description of what changes were made.\n\n### Basic Usage\n\nTo see a straightforward list of commits, simply use:\n\n\n```shell\n$ git log\n```\n\n\nYou will see an output similar to this:\n\n\n```shell\ncommit 9a3c6723ab6b9e4e2e9c9a5e4b5f1e321e5b926e\nAuthor: Jane Doe \nDate: Mon Oct 18 14:23:45 2023 -0400\n\n Fix bug in user authentication\n\ncommit 5e4b2a3c3b9a0e3b67d6a0b2d7a6f1b6e1f5c3a9\nAuthor: John Smith \nDate: Mon Oct 18 12:15:32 2023 -0400\n\n Add unit tests for user model\n```\n\n\n### Understanding the Output\n\nIn this example, the commit hash `9a3c6723ab6b9e4e2e9c9a5e4b5f1e321e5b926e` uniquely identifies the first commit. This hash is essential when you need to refer to specific commits later.\n\nEach log entry provides a snapshot of the project at the time of the commit. The **commit message** is particularly important; it often summarizes the changes made. A well-written commit message can save time later when you need to track down when and why changes were made.\n\n---\n\n# Customizing git log Output\n\nWhile the default output is useful, you can customize `git log` to display information according to your needs. Here are some common options:\n\n### Format Options\n\nUsing the `--pretty` flag, you can change how the output looks. For example:\n\n\n```shell\n$ git log --pretty=oneline\n```\n\n\nThis command condenses each commit to a single line, showing only the commit hash and message:\n\n\n```shell\n9a3c6723ab6b9e4e2e9c9a5e4b5f1e321e5b926e Fix bug in user authentication\n5e4b2a3c3b9a0e3b67d6a0b2d7a6f1b6e1f5c3a9 Add unit tests for user model\n```\n\n\n### Filtering Output\n\nYou can also filter the log based on several criteria:\n\n##### **By Author**:\n\n\n```shell\n$ git log --author=\"John Smith\"\n```\n\n\nThis shows commits made by \"John Smith\" only.\n\n##### **By Date**:\n\n\n```shell\n$ git log --since=\"2 weeks ago\"\n```\n\n\nThis retrieves commits from the last two weeks.\n\n### Combining Options\n\nYou can combine options to tailor the output further. For instance, to see a single line summary of commits from a specific author in the last month:\n\n\n```shell\n$ git log --author=\"Jane Doe\" --since=\"1 month ago\" --pretty=oneline\n```\n\n\n### Custom Log Formatting\n\nFor more tailored output, `git log` supports custom format strings using the `--pretty=format:` option. This allows you to specify exactly what information you want to see.\n\nFor example:\n\n\n```shell\n$ git log --pretty=format:\"%h - %an, %ar : %s\"\n\n3f6a9b1 - Alice, 2 minutes ago : Add input validation to signup form\na1b2c3d - Bob, 1 hour ago : Refactor user service into separate module\n9c8d7e2 - Charlie, 1 day ago : Fix typo in README\n```\n\n\nIn this command:\n\n- `%h` is the abbreviated hash\n- `%an` is the author name\n- `%ar` is the time since the commit (e.g., \"2 weeks ago\")\n- `%s` is the commit message\n\nThis provides a clean and informative layout. You can combine various placeholders to create your desired output.\n\n---\n\n# Visualizing Commit History\n\nSometimes, seeing a graphical representation of your commit history can be more insightful than a list. You can use the `--graph` option, which visualizes the branching and merging in your commit history.\n\n\n```shell\n$ git log --graph --oneline --decorate\n```\n\n\nThe `--oneline` flag condenses the output to a single line per commit, and `--decorate` adds branch names and tags to the output. The result will look like this:\n\n\n```shell\n* 3f6a9b1 (HEAD -> main, origin/main) Add checkout success message\n* a1b2c3d Merge branch 'feature/login'\n|\\ \n| * 9c8d7e2 (feature/login) Implement login validation\n| * 7b6a5c4 Add login form markup\n* | 5e4d3c2 Refactor header component\n|/ \n* 1a2b3c4 Initial project setup\n```\n\n\nThis output helps you quickly grasp the structure of your project history, revealing how branches and merges relate to each other.\n\n---\n\n# Exploring Changes with git log\n\n`git log` is not just about listing commits; it can show you what changes were made, too.\n\nBy appending the `-p` or `--patch` option, you can see the diffs for each commit.\n\n\n```shell\n$ git log -p\n```\n\n\nThis command will display each commit along with the changes introduced by that commit. The output might look like this:\n\n\n```shell\ncommit 9a3c6723ab6b9e4e2e9c9a5e4b5f1e321e5b926e\nAuthor: Jane Doe \nDate: Mon Oct 18 14:23:45 2023 -0400\n\n Fix bug in user authentication\n\ndiff --git a/auth.py b/auth.py\nindex e69de29..d95f3ad 100644\n--- a/auth.py\n+++ b/auth.py\n@@ -1,4 +1,4 @@\n-def authenticate(user):\n+def authenticate(user, password):\n```\n\n\nThis shows exactly what modifications were made in that specific commit, allowing you to understand the context and impact of the change.\n\n---\n\n# git shortlog\n\n`git shortlog` is a summary view of your commit history, grouped by author.\n\nInstead of listing every commit line by line like `git log`, it collapses them into a readable “who did what” view, often used for changelogs or contribution summaries.\n\n### Basic behavior\n\n\n```shell\n$ git shortlog\n```\n\n\nYou’ll see something like:\n\n\n```shell\nAlice Smity (3):\n Add login form validation\n Refactor auth middleware\n Fix typo in README\n\nBob Vance (2):\n Implement password reset endpoint\n Update API documentation\n```\n\n\n- Each author appears once.\n- Under their name, you see the subject lines of their commits.\n\nIf you only want to see the count of commits and not actual commit messages, you can use the flag `-s`.\n\n\n```shell\n$ git shortlog -s -n\n```\n\n\n**Sample Output:**\n\n\n```shell\n$ git shortlog -s -n\n\n25 Alice Smoth\n10 Bob Vance\n```\n\n\n- `-n` (numeric): sort by number of commits (most active first).\n\n---\n\nNow that you understand how to navigate and customize your commit history with `git log`, you are ready to explore the differences between commits using `git diff`.\n\nIn the next chapter, we will look at how to compare changes between commits and see what has been modified since your last commit.","pageType":"git"}

Viewing Commit History (git log)

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