Rebuilding Commit History by Changing Line Endings

Mandeep Singh -

Managing line endings in a codebase can often be a tricky endeavor, especially when collaborating across different platforms. Windows and Unix-like systems handle line endings differently, which can lead to issues when sharing code. Fortunately, there are tools available that can help us maintain consistency in our commit history when it comes to line endings. One such tool is git-filter-repo, which allows you to rewrite your repository's history with ease.

To get started, you need to install git-filter-repo. This tool is designed to replace the older git filter-branch command with a more efficient and simpler approach. You can find the installation instructions and prerequisites on its official GitHub page. After installation, ensure that it is added to your $PATH so that you can call it from the command line.

Once you have git-filter-repo set up, it’s essential to work on a fresh clone of your repository to avoid any accidental data loss. It’s also a good practice to back up your repository before proceeding with any history rewriting. You can create a backup by simply cloning your repository into a new directory.

The core of the process lies in running a command that specifies how to handle the file contents. Here’s a snippet of the command that you will need to execute:

git-filter-repo --file-info-callback '  
    contents = value.get_contents_by_identifier(blob_id)  
    ext = filename.lower().split(b".")[-1]  
    if ext not in [b"c", b"cpp", b"h", b"hpp"] or \  
            value.is_binary(contents):  
        # Make no changes to the file; return as-is  
        return (filename, mode, blob_id)  

    new_contents = contents.replace(b"\r\n", b"\n")  
    new_blob_id = value.insert_file_with_contents(new_contents)  

    return (filename, mode, new_blob_id)  
'

This command does a few things:

  • It retrieves the contents of each file identified by its blob_id.
  • It checks the file extension to determine whether it should modify the file. In this case, it targets only C and C++ files, ignoring binary files and others.
  • If the file qualifies for modification, it replaces Windows-style line endings ( ) with Unix-style line endings ( ).
  • Finally, it inserts the modified contents back into the repository.

This approach ensures that your commit history reflects the correct line endings without altering the integrity of your binary files or other types of files that shouldn't be affected.

For further reading on how to use git-filter-repo and its capabilities, refer to the official documentation. Understanding these commands can greatly enhance your ability to manage your codebase and keep it clean and consistent across different environments.