By default logrus uses these keys. If we also define one, logrus detects this
and then works around by adding 'fields.whatever' as the key name. However,
in the process of adding the key to the `Fields` it causes a race condition
which can crash the process with concurrent map r/w errors.
This is an attempt to fix#133.
Previously, we just clobbered the recent GUIDs with the lastest response
every single time, assuming that Atom/RSS feeds would consistently return the
same items. This appears to not be the case. In the wild, the number of items
returned on a single request can vary (sometimes even being 1 or 2 when usually
it is 50!).
This patch alters *how many* and *which* GUIDs we keep between requests, in an
attempt to prevent sending old news for buggy RSS feeds.
In the wild it looks like some RSS feeds will occasionally return 0 items
to requests *but not return an error*. This previously meant we would clobber
our knowledge of recent GUIDs with the empty set. This meant that the next
successful poll would resend the **entire** RSS feed.
Now broken down into:
- `labels` : Labelling/Unlabelling issues/PRs
- `milestones` : Milestoning/Demilestoning issues/PRs
- `assign` : Assigning/Unassigning issues/PRs
This is broken down in the guts of parsing the webhook event such that it
appears to be a unique `X-GitHub-Event` type.