feat: Add --compare-to option to override commit hash for incremental updates

[p0thi]

TL;DR

This PR adds a new --compare-to <commit-hash> CLI option to the generate command, allowing developers to explicitly specify the base commit to compare against when running incremental updates.

Description

Previously, incremental updates relied solely on the commit_id stored in metadata.json from the last generation run. This works well for local, continuous workflows but breaks down in CI/CD pipelines or after squashed PR merges, where the stored commit hash may no longer represent the correct baseline for detecting changes.

This pull request introduces a --compare-to flag that overrides the stored commit hash and uses a user-supplied commit as the diff baseline. When provided, the flag implicitly enables --update mode, so users do not need to pass both flags.

Key Changes:

• CLI Option (generate.py):

  • Added a new --compare-to <commit-hash> option to the generate command.
  • When set, it implicitly enables --update, simplifying the command invocation for CI/CD usage.

• Change Detection (generate.py):

  • Updated _detect_changed_files to accept an optional compare_to argument.
  • When compare_to is provided, it is used directly as prev_commit, bypassing the read of metadata.json and its stored commit_id.
  • Preserved the existing fallback behavior (reading from metadata.json) when --compare-to is not supplied.

• Documentation (README.md):

  • Added a usage example demonstrating codewiki generate --compare-to <commit-hash>, including a note that it is useful in CI/CD or squashed PR scenarios.