Problem

The current PUT /api/pullrequests/{id} endpoint expects a full PullRequest object. This causes:

• Risk of null values overwriting non-nullable fields like status
• Clients being forced to send unchanged or immutable fields (e.g. source, author)
• Redundant payloads and boilerplate in tests
• Poor ergonomics for UI and API consumers

Goal

Introduce a PATCH /api/pullrequests/{id} endpoint that:

• Accepts a lightweight DTO (PullRequestUpdateDto) with only mutable fields
• Performs a partial update by merging changes into the existing DB entity
• Prevents mutation of critical fields like id, author, source, target, issue, etc.
• Returns the updated PullRequest object

Example Request

PATCH /api/pullrequests/42
Content-Type: application/json

{
  "title": "Fix typo in title",
  "description": "Clarify PR scope"
}

Acceptance Criteria

•  Define PullRequestUpdateDto with fields:
  • String title
  • String description
  • (Possibly) PullRequestStatus status
•  Add new endpoint in controller:

  @PatchMapping("/{id}")
  public ResponseEntity<PullRequest> patchPullRequest(...)
  

•  Implement patch logic: load entity from DB, apply non-null fields from DTO, and persist
•  Validate that protected fields (e.g. author, source) remain unchanged
•  Add unit tests to verify:
  • Title-only patch
  • Description-only patch
  • Empty patch (no-op)
  • Invalid patch (e.g. null title when required)

Notes

This improvement avoids bloated update logic in tests and UI flows, and brings the API closer to best practices for partial updates.