Do not install multiple postgis version in the same docker image

[tcoupin]

Docker image should be as small as possible so one version of postgresql and one version of postgis.

Having multiple version is useful for integration tests against multiple environments.
For names, just follow officials images tag rules:

• latest, 10, 10.0, 10-pgis2.4, 10.0-pgis2.4, pgis2.4
• 9, 9.6, 9-pgis2.4, 9.6-pgis2.4
• 9-pgis2.3, 9.6-pgis2.3
• 9-pgis2.2, 9.6-pgis2.2
• ...

Multiple ways to achieve that:

• use the automated builds of hub.docker.com
  • 👍
    • already setup for your repo
    • use the "repository link" feature to rebuild postgis image on new official postgres image
  • 👎
    • configuration tag by tag, one dockerfile by (psql_version, pgis_version)
• use other CI platform like travis-ci.org
  • 👍
    • one dockerfile used with build-arg
    • just list matrix of (psql_version, pgis_version)
    • multi-arch build are possible (arm... )
  • 👎
    • no "repository link"

[mcanevet]

I'm not sure the gain in space worth the complexity added.
Moreover I think our dev sometimes want multiple versions of PostGis installed in the image.