Using git blame while ignoring revs

git blame shows the revision (commit) and author for each line modified in a file. This can be extremely useful when gathering context on why a particular change was made. However, sometimes you may want to ignore certain commits, especially if they involve formatting changes or large refactors that might obscure the history of who changed specific lines. This guide will explain how to effectively use the git blame --ignore-rev flag to ignore specific revisions.

Understanding git blame

The git blame command works by iterating through a file's change history to determine who last modified each line. However, some adjustments, lke formatting and style changes might obscure underlying functional changes. This is where ignoring specific revisions becomes useful.

Setting up ignore revs in git blame

The process to set up git blame to ignore specific revisions involves a few steps. These are crucial to ensure that you are only getting relevant information about the functional changes in your file.

Step 1: Identify the commits to ignore

Before modifying any configuration files, you need to decide which commits should be ignored by git blame. These are typically commits that refactor or reformat code without altering functionality.

Step 2: Creating a .git-blame-ignore-revs file

While you can ignore specific revisions individually with the ignore-rev flag, you can also specify multiple revisions to be ignored at once using a configuration file.

To do this, create a file in your repository where you can list all the commit hashes that should be ignored. A common naming convention for this file is .git-blame-ignore-revs.

Create this file by running the following commands:

# Navigate to your repository root
cd path/to/your/repo

# Create the .git-blame-ignore-revs file
touch .git-blame-ignore-revs

# Add the commit hashes of the revisions you wish to ignore
echo "commit_hash_here # Comment about why this commit is ignored" >> .git-blame-ignore-revs

Each commit hash is typically added to this file with a comment explaining why it is ignored. This is not only good practice for record-keeping but also helps maintain clarity in a team environment.

Step 3: Configuring git to use the ignore file

After populating the .git-blame-ignore-revs file with the commits you wish to ignore, you need to configure git to use this file when executing the git blame command.

# Set the blame.ignoreRevsFile configuration in your local git config
git config blame.ignoreRevsFile .git-blame-ignore-revs

This command tells git to reference the specified file for commits to ignore when you run git blame. This configuration can also be set globally or system-wide by using --global or --system.

Using git blame with ignored commits

Once you've configured git blame with the ignore-revs file, you can run git blame as you normally would:

git blame filename

With the configuration set, git blame will skip over the commits listed in the .git-blame-ignore-revs file, giving you a clearer picture of who made meaningful changes to the file.

Additional tips

• Review periodically: Over time, as more refactoring or formatting commits are added, it's a good practice to update the .git-blame-ignore-revs file.
• Sharing configurations: If you're working in a team, it's helpful to share the blame configuration settings by committing the .git-blame-ignore-revs file and ensuring everyone sets up their git config accordingly.

For further reading on git blame see the official Git documentation.