feat(platform): update pr baseBranch

[RahulGautamSingh]

Changes

• update the destination/target branch of existing prs when the basebranch is updated

Context

• Closes: update pr upon changing baseBranch #19900

Documentation (please check one with an [x])

• I have updated the documentation, or
• No documentation update is required

How I've tested my work (please select one)

I have verified these changes via:

• Code inspection only, or
• Newly added/modified unit tests, or
• No unit tests but ran on a real repository, or
• Both unit tests + ran on a real repository

[RahulGautamSingh]

Missing the code-changes for AWS CodeCommit.

[setchy]

Nice one @RahulGautamSingh 👏

[RahulGautamSingh]

There seems to be a problem.
The existingPRs won't get updated as baseBranch change doesn't come under title/body update so current ensurePr logic doesn't detect a change & skips the pr update. :)

renovate/lib/workers/repository/update/pr/index.ts

Lines 320 to 323 in 11b71b4

	if (
	existingPrTitle === newPrTitle &&
	existingPrBodyHash === newPrBodyHash
	) {

For this we will need to comapre the PR's target branch with the current base branch

Below are the 2 approaches I could think of:

1. Use cached baseBranch (not reliable as baseBranch might change sometimes in cache while PR isn't uppdated)
2. Use existing pr's targetBranch

I tried (2) but into an issue that the targetBranch (base.ref in case of github) isn't being fecthed. Do we need some code-change to get the target-branch when we fetch PR information using API?

[RahulGautamSingh]

Example PR info , github:

I got this as PR info from Github

{
  bodyStruct: {
    debugData: {
      createdInVer: '0.0.0-semantic-release',
      updatedInVer: '0.0.0-semantic-release'
    },
    hash: '596ef3415e2fa328b1473fe2f0fb633e63c39de8ba4db8810df72526adfb735e',
    rebaseRequested: false
  },
  createdAt: '2023-03-08T20:28:33Z',
  labels: [],
  node_id: 'PR_kwDOJGaIwM5Lmnld',
  number: 13,
  reviewers: [],
  sha: '23f17c06d283f7eeccf96851f7ab9b015950b0f1',
  sourceBranch: 'renovate/react-18.x',
  sourceRepo: 'RahulGautamSingh-testing/normalRepo',
  state: 'open',
  title: 'Update dependency react to v18',
  updated_at: '2023-03-08T20:28:33Z'
}

[rarkins]

"targetBranch" is an optional field in the Pr interface:

renovate/lib/modules/platform/types.ts

Line 75 in 01a1af5

targetBranch?: string;

[RahulGautamSingh]

targetBranch needs to added in the return object here.

renovate/lib/modules/platform/github/common.ts

Lines 10 to 22 in 67b076a

	export function coerceRestPr(pr: GhRestPr): GhPr {
	const bodyStruct = pr.bodyStruct ?? getPrBodyStruct(pr.body);
	const result: GhPr = {
	number: pr.number,
	sourceBranch: pr.head?.ref,
	title: pr.title,
	state:
	pr.state === 'closed' && is.string(pr.merged_at) ? 'merged' : pr.state,
	bodyStruct,
	updated_at: pr.updated_at,
	node_id: pr.node_id,
	};

Adding for github for now for testing and will do the same for other platforms if found missing.

[RahulGautamSingh]

This check will create issue for us when trying to update the targetBranch of a PR.

renovate/lib/workers/repository/update/branch/index.ts

Lines 201 to 205 in a3cc159

	if (
	branchIsModified ||
	(branchPr.targetBranch &&
	branchPr.targetBranch !== branchConfig.baseBranch)
	) {

Issue explanation:
When we update baseBranches in renovate-config the BranchConfig for all branches will have updated baseBranch but the targetBranch for existing PRs will be the older ones, thus they will differ and we will stop processing the PR.

Basically there are 2 cases:

1. baseBranch is updated -> ie. we need to update the pr targetBranch
2. user updates targetBranch manually -> ie. we mark the pr as edited

We need to handle the 2 cases differently by updating the if-check.

[rarkins]

Yes, the question is can we tell the difference between:

• Unchanged baseBranch, but the user changes target branch and wants us to leave it that way, versus
• Changed baseBranch, user wants us to change the target branch?

[viceice]

just remove from review list 😁

[RahulGautamSingh]

Blocked by: #21724