pr-mr-comment-update

name	pr-mr-comment-update
description	Use when the user asks to "update PR description", "update MR description", "analyze PR/MR changes and update comment", "summarize PR", "summarize MR", "generate PR/MR body from changes", or wants to automatically update a pull request or merge request description based on its code changes

PR/MR Description Update

Analyze all changes in a pull request (GitHub) or merge request (GitLab) and update the description/body with a comprehensive summary.

Quick Reference

Command	Description
/pr-comment-update	Analyze current branch PR/MR and update its description
/pr-comment-update 123	Analyze PR/MR #123 and update its description
/pr-comment-update owner/repo#123	Analyze PR/MR in specific repo (GitHub)
/pr-comment-update group/project#123	Analyze MR in specific project (GitLab)

Step 0: Detect Platform

Determine whether the repo uses GitHub or GitLab:

git remote get-url origin
# github.com → use gh commands
# gitlab.com or self-hosted GitLab → use glab commands

Workflow

digraph pr_update {
    rankdir=TB;
    node [shape=box];

    start [label="Start" shape=ellipse];
    detect [label="0. Detect platform\n(GitHub or GitLab)"];
    backup [label="0.5. Save original description\nto /tmp/pr|mr-N-original-description.md"];
    get_pr [label="1. Get PR/MR number\n(from arg or current branch)"];
    get_template [label="2. Check for PR/MR template"];
    get_diff [label="3. Get full diff"];
    get_commits [label="4. Get commit history"];
    analyze [label="5. Analyze changes"];
    format [label="6. Format description\n(using template if exists)"];
    update [label="7. Update PR/MR body"];
    check_title [label="8. Check PR/MR title\n(format + Jira ticket)"];
    done [label="Done" shape=ellipse];

    start -> detect;
    detect -> backup;
    backup -> get_pr;
    get_pr -> get_template;
    get_template -> get_diff;
    get_diff -> get_commits;
    get_commits -> analyze;
    analyze -> format;
    format -> update;
    update -> check_title;
    check_title -> done;
}

Step 0.5: Save Original Description

Before making any changes, save the current PR/MR description to /tmp/ so the user can restore it or reference the original later.

GitHub:

PR_NUMBER=$(gh pr view --json number --jq '.number')
gh pr view "$PR_NUMBER" --json body --jq '.body' > /tmp/pr-${PR_NUMBER}-original-description.md
echo "Saved original description to /tmp/pr-${PR_NUMBER}-original-description.md"

GitLab:

MR_NUMBER=$(glab mr view --output json | jq '.iid')
glab mr view "$MR_NUMBER" --output json | jq -r '.description' > /tmp/mr-${MR_NUMBER}-original-description.md
echo "Saved original description to /tmp/mr-${MR_NUMBER}-original-description.md"

Tell the user the backup path so they know where to find it if they want to restore or cherry-pick from the original.

Step 1: Get PR/MR Number

GitHub:

# If no PR number provided, get from current branch
gh pr view --json number --jq '.number'

# For cross-repo: gh pr view 123 -R owner/repo

GitLab:

# If no MR number provided, get from current branch
glab mr view --output json | jq '.iid'

# For cross-project: glab mr view 123 -R group/project

Step 2: Check for Template

GitHub:

cat .github/pull_request_template.md 2>/dev/null || echo "No template"

GitLab:

ls .gitlab/merge_request_templates/ 2>/dev/null || echo "No templates"
cat .gitlab/merge_request_templates/Default.md 2>/dev/null || echo "No default template"

Step 3: Get Full Diff

GitHub:

gh pr diff <PR_NUMBER>

# For large PRs, get file list first
gh pr view <PR_NUMBER> --json files --jq '.files[].path'

GitLab:

glab mr diff <MR_NUMBER>

# For large MRs, get file list first
glab api projects/:id/merge_requests/<MR_NUMBER>/changes --jq '.changes[].new_path'

Step 4: Get Commit History

GitHub:

gh pr view <PR_NUMBER> --json commits --jq '.commits[] | "\(.oid[0:7]) \(.messageHeadline)"'

GitLab:

glab api projects/:id/merge_requests/<MR_NUMBER>/commits --jq '.[] | "\(.short_id) \(.title)"'

Step 5: Analyze Changes

Review the diff and identify:

• Purpose: What does this PR/MR accomplish?
• Key changes: Major code modifications
• Files affected: Which areas of codebase
• Breaking changes: Any API or behavior changes
• Dependencies: New packages or version changes
• Tests: Test additions or modifications

Step 6: Format Description

Structure based on template if available, otherwise use:

## Summary
[1-3 bullet points describing what this PR/MR does]

## Changes
- [List key changes by category]

## Testing
[How the changes were tested]

## Notes
[Any additional context for reviewers]

If Jira ticket found in branch name or commits:

• Extract ticket key (e.g., PROJ-123)
• Add link at top: [PROJ-123](https://your-org.atlassian.net/browse/PROJ-123)

Step 7: Update Description

GitHub:

gh pr edit <PR_NUMBER> --body "$(cat <<'EOF'
<generated description here>
EOF
)"

GitLab:

glab mr update <MR_NUMBER> --description "$(cat <<'EOF'
<generated description here>
EOF
)"

Example Output

[AUTH-456](https://your-org.atlassian.net/browse/AUTH-456)

## Summary
- Add JWT-based authentication middleware
- Implement login/logout endpoints
- Add session management with Redis

## Changes

### New Features
- `POST /api/auth/login` - User login with email/password
- `POST /api/auth/logout` - Session invalidation
- `GET /api/auth/me` - Get current user info

### Security
- Password hashing with bcrypt (cost factor 12)
- JWT tokens with 24h expiration
- Rate limiting on auth endpoints

### Dependencies
- Added `jsonwebtoken@9.0.0`
- Added `bcrypt@5.1.0`

## Testing
- Unit tests for auth middleware
- Integration tests for login flow
- Manual testing with Postman

## Notes
- Requires `JWT_SECRET` environment variable
- Redis must be running for session storage

Step 8: Check PR/MR Title

After updating the description, always check whether the PR/MR title is correct. A bad title is easy to miss and looks unprofessional to reviewers.

Get the current title:

GitHub:

gh pr view <PR_NUMBER> --json title --jq '.title'

GitLab:

glab mr view <MR_NUMBER> --output json | jq -r '.title'

Expected format: TICKET-ID - Description

Example: INF-456 - Add S3 bucket module for data lake

Check for these issues:

Issue	Example of bad title	Fix
Missing ticket ID	Add S3 bucket module	Prepend ticket ID: INF-456 - Add S3 bucket module
Wrong separator	INF-456: Add S3 bucket	Use - (space-dash-space)
Ticket ID doesn't match branch	Branch is task.INF-456.foo, title has INF-789	Correct the ticket ID
Ticket ID at end or middle	Add S3 bucket INF-456	Move ticket ID to front
No description after ticket ID	INF-456	Add a meaningful description
Title is a commit message	fix typo	Replace with a proper summary

Determine the correct ticket ID by checking (in order):

1. Branch name pattern [type].[TICKET-ID].[description]
2. Commit messages in the PR/MR
3. The current title itself (if it already contains one)

If the title is correct: tell the user "Title looks good: <title>" and finish.

If the title needs fixing: propose the corrected title and ask the user to confirm before updating. Once confirmed, apply it:

GitHub:

gh pr edit <PR_NUMBER> --title "TICKET-ID - Description"

GitLab:

glab mr update <MR_NUMBER> --title "TICKET-ID - Description"

Common Issues

Issue	Solution
No PR for current branch (GitHub)	Run gh pr create first or specify PR number
No MR for current branch (GitLab)	Run glab mr create first or specify MR number
Permission denied	Ensure you have write access to the repository/project
Template not found	Use default format; check .github/ (GitHub) or .gitlab/merge_request_templates/ (GitLab)
Large diff timeout	Get file list first, then read key files individually
GitLab self-hosted	Set GITLAB_HOST env var or use --hostname flag with glab