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filter-branch

The git filter-branch command is a powerful tool for rewriting Git history. It allows you to rewrite branches by applying filters to each commit. This can be useful for tasks such as removing sensitive data, changing author information, or modifying file paths.

Detailed Explanation

  1. Rewriting History: git filter-branch can rewrite the commit history of a branch by applying specified filters to each commit. This can include modifying commit messages, changing file contents, or altering author information.

  2. Filters: There are several types of filters you can apply:

    • --tree-filter: Applies a shell command to the entire tree of each commit.

    • --index-filter: Applies a shell command to the index of each commit.

    • --env-filter: Modifies the environment variables for each commit.

    • --msg-filter: Modifies the commit message of each commit.

  3. Backup: By default, git filter-branch creates a backup of the original branch in the refs/original/ namespace. This allows you to recover the original history if needed.

  4. Performance: git filter-branch can be slow for large repositories because it processes each commit individually. For large-scale history rewriting, consider using tools like git filter-repo.

Examples

  1. Removing a File from History:

    git filter-branch --tree-filter 'rm -f path/to/file' -- --all

    This command removes path/to/file from the history of all branches.

  2. Changing Author Information:

    git filter-branch --env-filter ' if [ "$GIT_COMMITTER_EMAIL" = "old@example.com" ]; then GIT_COMMITTER_NAME="New Name" GIT_COMMITTER_EMAIL="new@example.com" GIT_AUTHOR_NAME="New Name" GIT_AUTHOR_EMAIL="new@example.com" fi ' -- --all

    This command changes the author and committer information for all commits where the email is old@example.com.

  3. Modifying Commit Messages:

    git filter-branch --msg-filter ' sed "s/Old Message/New Message/" ' -- --all

    This command replaces "Old Message" with "New Message" in all commit messages.

These examples demonstrate how git filter-branch can be used to rewrite Git history for various purposes.

Last modified: 29 November 2024
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