Optimize git object parsing with StringScanner

[kevmoo]

Migrates custom line-by-line reading logic in tag.dart and commit.dart to use native StringScanner capabilities with multiline regular expressions. This improves parsing robustness and performance.

Fixes handle edge cases including:

• Parsing multiline headers (e.g., PGP Signatures) correctly.
• Safely handling missing trailing blank lines and empty message bodies in rev-list outputs.

[gemini-code-assist]

Summary of Changes

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This pull request refactors the Git object parsing mechanisms, specifically for commits and tags, by replacing manual line-by-line string processing with the more efficient and robust StringScanner library. This change not only improves the performance of parsing operations but also addresses several edge cases related to multiline headers and the structure of Git object messages, leading to more accurate and reliable data extraction.

Highlights

• Optimized Object Parsing: Migrated custom line-by-line reading logic in tag.dart and commit.dart to leverage native StringScanner capabilities with multiline regular expressions, enhancing parsing efficiency.
• Improved Robustness: Enhanced parsing robustness, particularly for multiline headers (e.g., PGP Signatures) and edge cases involving missing trailing blank lines or empty message bodies in rev-list outputs.
• Refactored Regex: Updated the headerRegExp to correctly handle multiline headers by incorporating multiline matching and consuming line endings.

Changelog

• lib/src/commit.dart
  • Added a check to skip empty lines during commit parsing to prevent errors.
  • Refactored header parsing to use StringScanner.scan with the updated multiline headerRegExp.
  • Introduced logic to explicitly consume the blank line separating headers from the message body.
  • Updated message body parsing for rev-parse output to use StringScanner.scan with a regex that handles message lines and their termination.
• lib/src/tag.dart
  • Refactored header parsing to use StringScanner.scan with the new multiline headerRegExp.
  • Added a step to consume the blank line that separates tag headers from the message.
• lib/src/util.dart
  • Removed the StringScanner import as the custom extension is no longer needed.
  • Modified headerRegExp to support multiline header values and ensure it consumes the trailing newline.
  • Removed the StringScannerX extension and its associated _lineRegexp.

Activity

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Code Review

The pull request successfully migrates the custom line-by-line parsing logic in tag.dart and commit.dart to leverage the native StringScanner capabilities with multiline regular expressions. This change significantly improves the robustness and performance of parsing Git object data, especially for handling multiline headers and various edge cases related to message bodies and trailing blank lines. The removal of the custom readNextLine extension simplifies the codebase and aligns with the StringScanner's intended usage.