Using the blame command
by Jakub Narębski, Rasmus Voss, Aske Olsson, Ferdinando Santacroce
Git: Mastering Version Control
- Git: Mastering Version Control
- Table of Contents
- Git: Mastering Version Control
- Git: Mastering Version Control
- Credits
- Preface
- I. Module 1
- 1. Getting Started with Git
- 2. Git Fundamentals – Working Locally
- 3. Git Fundamentals – Working Remotely
- 4. Git Fundamentals – Niche Concepts, Configurations, and Commands
- Dissecting the Git configuration
- Configuration architecture
- Configuration levels
- Listing configurations
- Editing configuration files manually
- Setting up other environment configurations
- Basic configurations
- 5. Obtaining the Most – Good Commits and Workflows
- The art of committing
- Adopting a workflow – a wise act
- Summary
- 6. Migrating to Git
- 7. Git Resources
- II. Module 2
- 1. Navigating Git
- 2. Configuration
- 3. Branching, Merging, and Options
- 4. Rebase Regularly and Interactively, and Other Use Cases
- 5. Storing Additional Information in Your Repository
- 6. Extracting Data from the Repository
- 7. Enhancing Your Daily Work with Git Hooks, Aliases, and Scripts
- Introduction
- Using a branch description in the commit message
- Creating a dynamic commit message template
- Using external information in the commit message
- Preventing the push of specific commits
- Configuring and using Git aliases
- Configuring and using Git scripts
- Setting up and using a commit template
- 8. Recovering from Mistakes
- Introduction
- Undo – remove a commit completely
- Undo – remove a commit and retain the changes to files
- Undo – remove a commit and retain the changes in the staging area
- Undo – working with a dirty area
- Redo – recreate the latest commit with new changes
- Revert – undo the changes introduced by a commit
- Reverting a merge
- Viewing past Git actions with git reflog
- Finding lost changes with git fsck
- 9. Repository Maintenance
- Introduction
- Pruning remote branches
- Running garbage collection manually
- Turning off automatic garbage collection
- Splitting a repository
- Rewriting history – changing a single file
- Back up your repositories as mirror repositories
- A quick submodule how-to
- Subtree merging
- Submodule versus subtree merging
- 10. Patching and Offline Sharing
- 11. Git Plumbing and Attributes
- Introduction
- Displaying the repository information
- Displaying the tree information
- Displaying the file information
- Writing a blob object to the database
- Writing a tree object to the database
- Writing a commit object to the database
- Keyword expansion with attribute filters
- Metadata diff of binary files
- Storing binaries elsewhere
- Checking the attributes of a file
- Attributes to export an archive
- 12. Tips and Tricks
- III. Module 3
- 1. Git Basics in Practice
- An introduction to version control and Git
- Git by example
- Repository setup
- Creating a Git repository
- Cloning the repository and creating the first commit
- Publishing changes
- Examining history and viewing changes
- Renaming and moving files
- Updating your repository (with merge)
- Creating a tag
- Resolving a merge conflict
- Adding files in bulk and removing files
- Undoing changes to a file
- Creating a new branch
- Merging a branch (no conflicts)
- Undoing an unpublished merge
- Summary
- 2. Exploring Project History
- 3. Developing with Git
- 4. Managing Your Worktree
- Ignoring files
- File attributes
- Fixing mistakes with the reset command
- Stashing away your changes
- Managing worktrees and the staging area
- Multiple working directories
- Summary
- 5. Collaborative Development with Git
- 6. Advanced Branching Techniques
- Types and purposes of branches
- Branching workflows and release engineering
- Interacting with branches in remote repositories
- Summary
- 7. Merging Changes Together
- 8. Keeping History Clean
- An introduction to Git internals
- Rewriting history
- Amending history without rewriting
- Summary
- 9. Managing Subprojects – Building a Living Framework
- Managing library and framework dependencies
- Managing large Git repositories
- Summary
- 10. Customizing and Extending Git
- 11. Git Administration
- 12. Git Best Practices
- 1. Git Basics in Practice
- A. Bibliography
- Index
- Configuration architecture
- Dissecting the Git configuration
The bisect command is good when you don't know where in your code there is a bug, but you can test for it and thereby find the commit that introduced it. If you already know where in the code the bug is but want to find the commit that introduced it, you can use git blame. The blame command will annotate every line in the file with the latest commit that touched that line, making it easy to find the commit ID and then the full context of the commit.
We'll use the same repository and branch as in the bisect example:
$ git clone https://github.com/dvaske/cookbook-tips-tricks.git $ cd cookbook-tips-tricks $ git checkout bug_hunting
We know that the bug is in map.txt on lines 37-39. To annotate each line in the file with the commit ID and author, we'll run git blame on the file. We can further limit the search to specific lines with the -L <from>,<to> option:
From the output, it can be clearly seen that the commit with the ID 83c22a39 by HAL 9000 introduced the bug.
The blame command can be used even if the file has been refactored and the code has been moved around. With the -M option, the blame command can detect lines that have been moved around in the file and with the -C option, Git can detect lines that were moved or copied from other files in the same commit. If the -C option is used three times -CCC, the blame command will find lines that were copied from other files in any commit.
-
No Comment