How to make Git automatically remove trailing white space before committing?

When using Git for version control, ensuring code quality is a crucial aspect. Automatically removing trailing whitespace is a common practice that helps maintain code cleanliness and avoids unnecessary changes. To achieve this, we can leverage Git's pre-commit hook functionality. Below are the specific steps and examples:

Step 1: Create or Modify the pre-commit Hook

In your Git repository, the .git/hooks/ directory contains sample hook scripts that you can use to customize Git's behavior. First, ensure that there is a script file named pre-commit.

If this file does not exist, you can create it:

bash
cd your-repository/.git/hooks
touch pre-commit   # Create the file
chmod +x pre-commit  # Make the script executable

Step 2: Write a Script to Remove Trailing Whitespace

Open the pre-commit file and write a script to check the files about to be committed and automatically remove trailing whitespace from them. Here is a simple example using a shell script:

bash
#!/bin/sh

# Identify the staged files
STAGED_FILES=$(git diff --cached --name-only --diff-filter=ACMR)

# Check and fix trailing whitespace
for FILE in $STAGED_FILES; do
  # Only operate on certain file types, such as .py and .txt
  if [[ "$FILE" =~ \.py$|\.txt$ ]]; then
    sed -i '' -e's/[[:space:]]*$//' "$FILE"
    # Re-add changes to the staging area
    git add "$FILE"
  fi
done

# Continue the commit process
exit 0

Step 3: Test the Hook

In your local repository, modify some files, intentionally adding trailing whitespace, and then attempt to commit these changes. The expected result is that the trailing whitespace is automatically removed, and the changes are included in the commit.

Notes

• Ensure your script is compatible with your operating system. For example, the sed command used above behaves slightly differently on Linux and macOS.
• Thoroughly test your script to ensure it does not affect code logic or delete incorrect content.
• This method is only applicable to local repositories. If working in a team, each member must set up this hook in their local environment.

By doing this, we can ensure that code cleanup is automatically performed before each commit, maintaining the cleanliness and consistency of the codebase.