Get the Mergeable status of the PR before updating the
Status. This allows for the Status to be a required
Status for merging the PR. This allows us to use the
atlantis status as a Required status, which is the
configuration often used, since most deployments
want to ensure tf plans have all been successfully
applied before merging
Issue: https://github.com/runatlantis/atlantis/issues/453
Automerging merges pull requests automatically if all plans have been
successfully applied.
* Save status of PR's to BoltDB so after each apply, we can check if
there are pending plans.
* Add new feature where we delete successful plans *unless* all plans
have succeeded *if* automerge is enabled. This was requested by users
because when automerge is enabled, they want to enforce that a pull
request's changes have been fully applied. They asked that plans not be
allowed to be applied "piecemeal" and instead, all plans must be
generated successfully prior to allowing any plans to be applied.
Introduce new `mergeable` requirement, in similar vein to the `approved`
requirement. Ran `make go-generate` to update mocks accordingly.
This addresses issue #43.
