Document git history of flush() call in Forwarder.sol fallback function

[Copilot]

The problem statement requested historical analysis of when line 72 in Forwarder.sol (the flush() call within fallback()) was introduced.

Key Findings

Initial Implementation (August 3, 2020)

• Commit: fb24dd6ac2fb3c70dad0266995dd4d4b5605bcae
• Used external call syntax: this.flush()

Current Implementation (January 7, 2021)

• Commit: c5ae39ad15345ee5f1ed90e89bfbda18b84f605d
• Changed to internal call: flush()
• Fixed event emission bug where msg.sender was incorrectly set to proxy address instead of original sender
• Changed function visibility from external to public to enable internal calls

// Before (August 2020)
fallback() external payable {
    this.flush();  // External CALL changes msg.sender
}

// After (January 2021)
fallback() external payable {
    flush();  // Internal call preserves msg.sender
}

Documentation Added

Created FLUSH_FUNCTION_HISTORY.md with complete git history, commit details, and technical explanation of the proxy-based architecture issue that necessitated the change.

Original prompt

On Forwarder.sol:72-72, When was this line introduced where we call the flush function when we receive funds

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