Don't spam users with PR build results

[atrocities]

Relatively low priority:

Stashbot currently makes new a new comment on the pull request whenever a new build finishes, regardless of whether the result is the same as, or different from, the last build result. This results in a lot of email noise when a user is involved in many PRs, which is frequently the case. Ideally, it would only email users when the build breaks, or goes from a 'passing' status to a 'breaking' status.

Since it doesn't seem like there's a better way to keep state for PR builds, maybe do some research to figure out whether or not it's possible to not send out emails whenever a comment is made on a PR.

[atrocities]

Alternatively, Stashbot could read the last comment and simply not comment again if the state did not change.

This could be toggled on/off via a configuration option.

[terabyte]

There is already some metadata where the state of the PR is tracked. It should be possible to know from this whether or not the state has changed. If the state hasn't changed, when the comment is made, we'd like to say "don't fire notifications on this comment". In BuildSuccessReportingServlet see lines 224-232 or so for where I update the metadata. The comment is made around line 277, and if you look at PullRequestCommentAddOperation, you will see it calls PullRequestService.addComment(repo_id, pr_id, comment_text).

https://developer.atlassian.com/static/javadoc/stash.old-perms-pre-feb4/1.3.0/api/reference/com/atlassian/stash/pull/PullRequestService.html#addComment%28int,%20long,%20java.lang.String%29

The problem is, we definitely want to make the comment, and I'm not sure if we can prevent the notification from being sent. I seem to recall an addComment API that took a boolean value for whether or not notifications should be sent, but I can't find it now, perhaps I was dreaming.

Stash notifications are very immature and not very customizable. I've actually been working on a custom plugin to completely replace stash notifications but I wouldn't bet the farm on that solving your problem either.