Link pull requests that will close open GitHub issues to the relevant Code Corps tasks

[joshsmith]

Problem

We need to parse the body that GitHub returns to us in pull requests using their closing keywords in order to connect our tasks to these PRs in our UI.

[begedin]

This would involve a model linking a Task to a PR.

We can handle a PR webhook and parse its body to look for these keywords, but without a model to store the inferred link in, there would be no way that I can think off to show this when viewing the task on CodeCorps.

At a bare minimum, we would need a field on the Task

If we decide to go as far as having a GithubPullRequest model, then it would make sense to start with having a GithubIssue model first, instead of linking the PR to our Task directly.

[begedin]

• parse body for closing keywords, extract github ids
• if they exist, find github issues (or pull requests) with those ids, associate with tasks belonging to those issues, dissasociate form tasks belonging to other github issues
• if none are found, disassociate from associated tasks which do belong to github issues

The special case is when we get a pr created which does not close any issues. In that case, my suggestion is we

• create a codecorps task, which is linked to the pr, but not to a github iusse
• we leave that task associated from now on, regardless of new associations being added/removed

My philosophy is, that one was created on CC and can potentially hold information that will be lost, if we disassociate. Maybe at some point in the future, we allow "converting the PR to a github issue", which would associate that task with a github issue as well. At that point, it can behave like a normal task, but until that point, we shouldn't assume and try to avoid any automatons with it. If the PR has been linked to an issue since, let the user close the original task we've created if they want to.

[begedin]

It's become slightly less clear to me how we want to approach pull requests

Right now, the develop branch works without looking at pull request body to link to closing issues. Effectively, each github pull request always gets a codecorps task of its own.

However, based on #1004 we want behavior that's at least in part similar to github - a pull request can also be linked to one or more other issues, which it close, or at least referrs to.

My assumption was, a pull request gets a task of its own, only if it doesn't close an issue (which would also have a task on its own). It seems like my assumption might be wrong in this.

Would the following be the correct approach?

• a pull request always gets a codecorps task of its own, regardless of being connected to an issue or not
• a pull request might also be a closing pull request to several other github issues (and thus, codecorps tasks), meaning those tasks will also belong to that pull request

[begedin]

Depending on our conversation in #1082, it looks like we need a many-to-many relationship between Task and PullRequest.

We should discuss a solution there before we can tackle this.

[joshsmith]

Looks like the following is what we'll need:

schema "github_issues" do
  has_many :github_issue_refers_to
  has_many :github_issue_referred_by
end

schema "github_issue_references" do
  belongs_to :referred_by
  belongs_to :refers_to
  field :type :string # regular, closing
end