1072: Skara should validate the commit hash of a Backport PR

[erikj79]

Add a check for "Backport " titles that the given hash isn't the head of the PR itself. If the user mistakenly uses that hash, Skara is very likely to get fooled into thinking the backport is clean.

While investigating this, I also discovered that the CheckWorkItem was inconsistent with not repeating "backport" errors, so I implemented a general mechanism for this, which guarantees that the same exact error message is never repeated. I believe this will be good enough, and certainly better than the existing behavior.

---

Progress

• Change must not contain extraneous whitespace
• Change must be properly reviewed

Issue

• SKARA-1072: Skara should validate the commit hash of a Backport PR

Reviewers

• Kevin Rushforth (@kevinrushforth - Reviewer) ⚠️ Review applies to f0cfcff

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.java.net/skara pull/1184/head:pull/1184
$ git checkout pull/1184

Update a local copy of the PR:
$ git checkout pull/1184
$ git pull https://git.openjdk.java.net/skara pull/1184/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 1184

View PR using the GUI difftool:
$ git pr show -t 1184

Using diff file

Download this PR as a diff file:
https://git.openjdk.java.net/skara/pull/1184.diff

[bridgekeeper]

👋 Welcome back erikj! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[mlbridge]

Webrevs

• 02: Full - Incremental (bb129b9e)
• 01: Full - Incremental (f0cfcfff)
• 00: Full (136cb2fc)

[erikj79]

As we found another instance of this issue, that instance highlighted another, related, problem. If a proposed backport (or any change for that matter, but backports seem more likely) has already been done, basically making the changes in the PR redundant when merged with the target, this wasn't handled well today. I have added a check for this as well.

[kevinrushforth]

Looks good.

Did you want to add a test where the specified backport hash was a commit in the PR other than the head?

[openjdk]

@erikj79 This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

🔍 One or more changes in this pull request modifies files in areas of the source code that often require two reviewers. Please consider if this is the case for this pull request, and if so, await a second reviewer to approve this pull request before you integrate it.

After integration, the commit message for the final commit will be:

1072: Skara should validate the commit hash of a Backport PR

Reviewed-by: kcr

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been no new commits pushed to the master branch. If another commit should be pushed before you perform the /integrate command, your PR will be automatically rebased. If you prefer to avoid any potential automatic rebasing, please check the documentation for the /integrate command for further details.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

[erikj79]

Added test as asked.

[erikj79]

/integrate

[openjdk]

@erikj79 Pushed as commit 5b081a7.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.