Use three-dot comparison to exclude merge commits from "changes since last review"

[Copilot]

When viewing "changes since last review", merge commits were included in the diff. GitHub's web UI excludes these by using three-dot comparison syntax.

Changes

• src/github/loggingOctokit.ts: Added excludeMergeCommits parameter to compareCommits(). When true, uses three-dot syntax (base...head) via compareCommitsWithBasehead endpoint. When false (default), uses standard compareCommits endpoint with separate base and head parameters.

• src/github/pullRequestModel.ts: Pass showChangesSinceReview flag to compareCommits() to enable merge commit filtering

Technical Detail

GitHub API comparison modes:

• Standard comparison (separate base/head parameters): Shows all changes between commits, including merge commits. This is the default behavior.
• Three-dot (...): Changes unique to head since common ancestor, excluding merge commits. Only supported via the basehead parameter format.

Note: The GitHub API does not support two-dot (..) notation. The standard comparison using separate base and head parameters is equivalent to a two-dot comparison behavior, while three-dot syntax must be explicitly used via the basehead parameter.

The three-dot comparison naturally filters out changes brought in by merge commits (e.g., merging main into a feature branch), matching web UI behavior.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Hide merge commits from "changes since last review"</issue_title>
<issue_description>

Like with the web view, changes from merge commits shouldn't be shown when viewing changes since the last review.</issue_description>

<agent_instructions>Pay special attention to this comment: #4510 (comment)</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes Hide merge commits from "changes since last review" #4510

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[alexr00]

@copilot GitHub doesn't appear to support '..'.

[Copilot]

You're absolutely right! The GitHub API only supports three-dot notation (...), not two-dot (..). I've updated the implementation to:

• Use the standard compareCommits API with separate base and head parameters for the default comparison
• Only use three-dot syntax (...) via compareCommitsWithBasehead when excluding merge commits

Fixed in commit 47a70ef.