feat(github): update pr baseBranch

[RahulGautamSingh]

Changes

• update base of an existing update PR when baseBranch is changed in config

Context

• Part of: update pr upon changing baseBranch #19900
• Resolves: Prevent renovate from ever merging PRs laminas/.github#44

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]

Reproduction:
RahulGautamSingh-testing/update-base-branch#3 (baseBranch changed in config)
RahulGautamSingh-testing/update-default-branch-0#1 (defaultBranch changed)

[viceice]

we need to save the original base branch inside cache or body struct, so we can detect a manual changed PR target by users and don't overwite it.

we also need to open follow up PR's for other platforms.

[RahulGautamSingh]

we need to save the original base branch inside cache or body struct, so we can detect a manual changed PR target by users and don't overwite it.

Already done here: #21724

we also need to open follow up PR's for other platforms.

Working on it.

[rarkins]

The basic use case works as expected, however the logs are misleading:

DEBUG: Processing existing PR (repository=renovate-reproductions/22663, branch=renovate/node-18.x)
DEBUG: PR body changed (repository=renovate-reproductions/22663, branch=renovate/node-18.x)
       "prTitle": "Update Node.js to v18.16.0"
DEBUG: updatePr(1, Update Node.js to v18.16.0, body) (repository=renovate-reproductions/22663, branch=renovate/node-18.x)
DEBUG: PR updated...prNo: 1 (repository=renovate-reproductions/22663, branch=renovate/node-18.x)
 INFO: PR updated (repository=renovate-reproductions/22663, branch=renovate/node-18.x)
       "pr": 1,
       "prTitle": "Update Node.js to v18.16.0"

There's not a single mention of the old base branch or what's going on. Can you print an explicit message which says "PR base branch has changed" or something similar?

[renovate-release]

🎉 This PR is included in version 35.126.0 🎉

The release is available on:

• GitHub release
• 35.126.0

Your semantic-release bot 📦🚀