Add GitHub action to automatically create a port PR (based on label) & minor bug fixes

[tdonohue]

References

• Ports the recent backend GitHub Actions updates to the frontend codebase
• Includes code from Add GitHub action to automatically create a port PR (based on label) DSpace#8988 and Bug fixes for actions: Run PR porting action as 'dspace-bot'. Ignore errors from label_merge_conflicts DSpace#8994 and Fix typo. Config must be a valid regex DSpace#8995

Description

Main feature is to add a custom PR port action to automatically port PRs to other branches (depending on the label).

How it works

Suppose a PR is created against main and labeled with port to dspace-7_x (this label needs to be created).

1. When that PR is merged, this new action will trigger.
2. Because the merged PR has the port to dspace-7_x label, this action will attempt to create a new PR against the dspace-7_x branch with the same commits (cherry-picked) as the main PR.
3. Assuming the new PR can be created, it will be linked back to the original PR via a comment. At this point, we can wait for the PR to pass tests & then merge immediately.
4. If the new PR fails to be created, then a comment will be added to the original PR which says it failed. At this point, we'd have to do a manual port.
   (NOTE: This same process will also work if the original PR was created against dspace-7_x and the PR is labeled with port to main)

Here's an example that I tried with a test repo:

• Installed this backport-action and configured it.
• Created two branches in the repo. The main branch and a maintenance branch. Ensured they started out synced.
• Created a tiny PR to make two commits to the README: Create README.md tdonohue/test_actions#12
  • Notice this PR was given the port to maintenance label.
• Once that PR 12 was merged, this PR was auto-created against the maintenance branch: [Port maintenance] Create README.md tdonohue/test_actions#13
  • Notice this new PR has the same two commits as the original PR
• A comment linking to the new PR was auto-created in the original PR: Create README.md tdonohue/test_actions#12 (comment)

SEE ALSO description in DSpace/DSpace#8988

[tdonohue]

Merging immediately to sync DSpace/dspace-angular with DSpace/DSpace

[dspace-bot]

Successfully created backport PR for dspace-7_x:

• [Port dspace-7_x] Add GitHub action to automatically create a port PR (based on label) & minor bug fixes #2407