RFR: 1937: Re-evaulate all PRs when .jcheck/conf changes

[Zhao Song]

On Mon, 12 Jun 2023 23:26:53 GMT, Zhao Song <zsong at openjdk.org> wrote:

> As Erik said in the issue: "When we bump the version in .jcheck/conf from N to N+1 in the jdk master branch, PRs with CSRs are often not updated to reflect this."
> 
> This root cause of this is that changing of .jcheck/conf in target ref of the pr will not be able to trigger checkWorkItem for this pr.
> 
> In this patch,
> 1. The prBot will monitor the changes to the .jcheck/conf file in any branch(except for PR branches).
> 2. If the prBot detects an update to the .jcheck/conf file in a branch, it will trigger a checkWorkItem for all open PRs whose target ref is the branch where the .jcheck/conf file was updated.
> 3. To solve the problem related with bot restarting, the contents of the .jcheck/conf file in the target branch of a PR will be included in the metadata hash.

bots/pr/src/main/java/org/openjdk/skara/bots/pr/PullRequestBot.java line 189:

> 187:                 .map(HostedBranch::name)
> 188:                 .filter(name -> !name.startsWith("pr/"))
> 189:                 .toList();

Currently, fetching all existing branches is the main overhead in this feature. It takes about 2s for JDK repo. If this overhead is not acceptable, the other way to solve this is store the branches in bot config.

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PR Review Comment: https://git.openjdk.org/skara/pull/1531#discussion_r1228411715