move ci/logstash_releases.json

[kares]

from logstash's repo ... here to be tracked by the .ci repo itself

some period when its in both might be necessary -> or a HTTP MOVED if curl handles that

[yaauie]

Related, but potentially a tangent.

We can also take advantage of travis's Build Config Imports, which could allow us to maintain a source of truth in a single external repository.

With the existing tooling to resolve MAJOR.x in each plugin, I would imagine having shared configs that look like:

matrix:
  include:
    - ELASTIC_STACK_VERSION=6.x
    - ELASTIC_STACK_VERSION=7.x
    - ELASTIC_STACK_VERSION=7.x SNAPSHOT=true
    - ELASTIC_STACK_VERSION=6.x SNAPSHOT=true

-- logstash-plugins/.ci:travis-include/supported-builds.travis.yml@master

(we could provide similar for INTEGRATION=true variants for plugins that need )

Which could be used in travis configs in individual repos with:

version: ~> 1.0
import:
 - source: logstash-plugins/.ci:travis-include/supported-builds.travis.yml@master

-- logstash-plugins/$plugin:.travis.yml

OR, we could skip the complexities of having each plugin resolve MAJOR.x and just include specific versions in a shared config that we import, giving us a single source of truth.