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November 9, 2023 14:36
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Replaces a target commit with multiple smaller commits
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| #!/usr/bin/env python3 | |
| """ | |
| Replaces a target commit with multiple smaller commits and then reapplies | |
| the subsequent commits on top of it. The original commit is split by each changed file, and then subsequent | |
| commits are cherry-picked on top of the new split commits. | |
| It's useful to fine-grain a `git bisect` to find a problematic change. | |
| Usage: | |
| git split-commit <commit> | |
| """ | |
| import subprocess | |
| import argparse | |
| def split_commit(commit_hash): | |
| # Find all commits after the target commit up to the original HEAD. | |
| original_head = subprocess.check_output(['git', 'rev-parse', 'HEAD'], text=True).strip() | |
| subsequent_commits = subprocess.check_output( | |
| ['git', 'log', '--first-parent', '--format=%H', f"{commit_hash}..{original_head}"], text=True).strip().split("\n") | |
| subsequent_commits = reversed([commit for commit in subsequent_commits if commit]) | |
| # Checkout to a new temporary branch based on the commit before the target commit. | |
| subprocess.run(['git', 'reset', '--hard', f"{commit_hash}^"], check=True) | |
| start_range = subprocess.check_output(['git', 'rev-parse', 'HEAD'], text=True).strip() | |
| # Cherry-pick the target commit but do not commit, keeping changes in the index. | |
| subprocess.run(['git', 'cherry-pick', '--no-commit', commit_hash], check=True) | |
| # Get the list of files that were part of the target commit. | |
| files_changed = subprocess.check_output(['git', 'diff', '--cached', '--name-only'], text=True).strip().split('\n') | |
| # Commit each file individually. | |
| for file in files_changed: | |
| print(f"Committing {file}...") | |
| subprocess.run(['git', 'reset', '--', '.'], check=True) | |
| subprocess.run(['git', 'add', '--', file], check=True) | |
| subprocess.run(['git', 'commit', '-nm', f"Split change from {commit_hash}: {file}"], check=True) | |
| # Cherry-pick each subsequent commit. | |
| for commit in subsequent_commits: | |
| try: | |
| subprocess.run(['git', 'cherry-pick', commit], check=True) | |
| except subprocess.CalledProcessError: | |
| # is a merge? | |
| subprocess.run(['git', 'cherry-pick', '-m', '1', commit], check=True) | |
| print(f"Replaced commit {commit_hash} with multiple smaller commits and reapplied subsequent commits.") | |
| print(f"You can start git bisect in {start_range} ") | |
| if __name__ == "__main__": | |
| parser = argparse.ArgumentParser(description=__doc__) | |
| parser.add_argument('commit_hash', type=str, help='The hash of the commit to split.') | |
| args = parser.parse_args() | |
| # Call the function with the provided commit hash. | |
| split_commit(args.commit_hash) |
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