Documentation: InvokeAI PR review and merge policy

docs/contributing/PR-MERGE-POLICY.md

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+# Pull Request Merge Policy
+
+This document outlines the process for reviewing and merging pull requests (PRs) into the InvokeAI repository.
+
+## Review Process
+
+### 1. Assignment
+
+One of the repository maintainers will assign collaborators to review a pull request. The assigned reviewer(s) will be responsible for conducting the code review.
+
+### 2. Review and Iteration
+
+The assignee is responsible for:
+- Reviewing the PR thoroughly
+- Providing constructive feedback
+- Iterating with the PR author until the assignee is satisfied that the PR is fit to merge
+- Ensuring the PR meets code quality standards, follows project conventions, and doesn't introduce bugs or regressions
+
+### 3. Approval and Notification
+
+Once the assignee is satisfied with the PR:
+- The assignee approves the PR
+- The assignee alerts one of the maintainers that the PR is ready for merge using the **#request-reviews Discord channel**
+
+### 4. Final Merge
+
+One of the maintainers is responsible for:
+- Performing a final check of the PR
+- Merging the PR into the appropriate branch
+
+**Important:** Collaborators are strongly discouraged from merging PRs on their own, except in case of emergency (e.g., critical bug fix and no maintainer is available).
+
+### 5. Release Policy
+
+Once a feature release candidate is published, no feature PRs are to
+be merged into main. Only bugfixes are allowed until the final
+release.
+
+## Best Practices
+
+### Clean Commit History
+
+To encourage a clean development log, PR authors are encouraged to use `git rebase -i` to suppress trivial commit messages (e.g., `ruff` and `prettier` formatting fixes) after the PR is accepted but before it is merged.
+
+### Merge Strategy
+
+The maintainer will perform either a **3-way merge** or **squash merge** when merging a PR into the `main` branch. This approach helps avoid rebase conflict hell and maintains a cleaner project history.
+
+### Attribution
+
+The PR author should reference any papers, source code or
+documentation that they used while creating the code both in the PR
+and as comments in the code itself. If there are any licensing
+restrictions, these should be linked to and/or reproduced in the repo
+root.
+
+
+## Summary
+
+This policy ensures that:
+- All PRs receive proper review from assigned collaborators
+- Maintainers have final oversight before code enters the main branch
+- The commit history remains clean and meaningful
+- Merge conflicts are minimized through appropriate merge strategies