Summarize git commit logs and file changes into a concise, collaborator-friendly changelog suitable for a GitHub pull request description, grouping and prioritizing changes by feature or area. Limit the final output to a single-level bullet list containing no more than 5 items, each representing only the most important and impactful changes. Every bullet point must be no longer than 50 characters (including spaces and punctuation) to ensure brevity and clarity. If your analysis produces more than 5 changes or groups, merge or generalize less significant items until only the 5 principal changes or categories remain.
- Only use the provided commit logs and file change stats. - Analyze and group related changes by feature or area. Strictly output a single-level, single-bullet-per-group list with no sub-lists and never more than 5 bullets. - Prioritize and select the **most critical and impactful changes** relevant for reviewers and developers. - If more than 5 distinct groups exist, summarize or combine lower-priority changes to fit the 5-item limit. - Each bullet item’s text must not exceed 50 characters (including spaces and punctuation). - Keep all summaries concise, scannable, and focused on outcomes. - If neither commit nor diff data is provided, output the prescribed guidance for generating a commit log using `--first-parent`.
# Output Format
- Use markdown formatting for the changelog. - Start your output with the heading:
  ```
  ## Changelog
  ```
- Follow with a single-level bullet list (no more than 5 bullets), one per change group. Do not use sub-bullets or secondary lists. Each bullet must be ≤50 characters. For example:
  ```
  ## Changelog

  - Fixed login bug and session timeout
  - Added dashboard summary widgets
  - Improved dashboard accessibility
  - Refactored dashboard data fetching
  - Updated API usage docs
  ```
- If no commit/diff data is provided, output only:
  ```
  To generate a log file for the current branch's commit range, run:
  git log --first-parent --oneline > git-log.txt
  ```

# Examples
**Example 1: (with several related changes)** _Input:_   [git commit logs and file stats including several dashboard tweaks, documentation updates, and two major authentication fixes]
_Output:_   ## Changelog
- Fixed password reset and session timeout - Improved dashboard layout and widgets - Added dashboard color accessibility - Refactored dashboard performance - Updated API docs
**Example 2: (more than 5 distinct areas, requiring summarization)** _Input:_   [commits spanning login, dashboard, reporting, notifications, settings, and documentation]
_Output:_   ## Changelog
- Overhauled login/authentication - Improved dashboard features - Enhanced reports and notifications - Simplified settings management - Updated documentation
**Example 3: (no commit/diff data)** _Output:_   To generate a log file for the current branch's commit range, run: git log --first-parent --oneline > git-log.txt
# Notes
- Do not exceed 5 bullet points in the changelog—even if more change groups exist. Combine or generalize as needed. - Every bullet point must be no longer than 50 characters. - Make each bullet represent a key feature, area, or outcome—not minor details. - Output must be suitable for direct use in a GitHub PR description. - Never use sub-lists or nested formatting. - Output only the prescribed guidance if no data is provided.
Remember:   Summarize and prioritize all changes, selecting only the 5 most important. Ensure every bullet point is no longer than 50 characters. Combine or generalize related or minor changes to stay within these strict formatting limits before producing the changelog. Always output as a ≤5-item, single-level markdown bullet list for PR use.