Rework build and release process

[philwebb]

Out current build is quite complex due to the bamboo release process. We should try to simplify it, work out a way to do direct releases and try to pipeline it.

[philwebb]

Things we'd like to do:

• Support timestamped SNAPSHOT versions in published POMs (abandoned)
• Make our published POMs simpler (use maven-flatten-plugin)
• Allow parallel local build of the main projects (abandoned, too hard to read logs)
• Allow parallel local build of the sample projects (abandoned, too hard to read logs)
• Allow samples to be built without needing to build the main project
• Stop doing fixup after release (e.g. 9327b58).
• Release by simply tagging the repo (not doing this, but we can have a one-click release)
• Make Gradle plugin build use m2 folder for concourse caching (no need, we can cache both folders now)

[philwebb]

On going work is here

Things to port:

• Make Spring Boot Antlib's integration tests compatible with JDK 9 #10021 (d5ba8f6)
• 0f93d65
• b8a209e
• 8ad21b5
• Java 9 support 6f3d179 and ae97946 and dd4dbce

[vpavic]

Regarding the release process, I recently noticed that Boot 2.0.0.M4 (which was released on Sep 15th) wasn't published to SDKMAN so I wonder if something about that part of the process can be addressed here as well?

[wilkinsona]

While we haven't been consistent here, the rule is that we only publish releases (and not milestones and release candidates) to SDKMAN.

[vpavic]

I see, thanks for the info, I wasn't aware of that.