For the details about this PR, please see the blog post https://eed3si9n.com/sbt-remote-cache/.
* Add cache basics
* Refactor Attributed to use StringAttributeMap, which is Map[StringAttributeKey, String]
* Implement disk cache
* Rename Package to Pkg
* Virtualize packageBin
* Use HashedVirtualFileRef for packageBin
* Virtualize compile task
Problem
-------
In sbt 1, platform cross building is implemented using in the user-land
using `%%%` operator, which clevery handles both Scala cross building
and appending platform suffix like sjs1.
However, in general symbolic `%%%` is confusing, and hard to explain.
Solution
--------
In sbt 2, we should subsume the idea of platform cross building,
so `%%` can act as the current `%%%` operator.
This adds a new setting called `platform`, which defaults to
`Platform.jvm` by default.
When a subprojects sets it to `Platform.sjs1`, `ModuleID`s defined using
`%%` operator will inject the platform suffix `_sjs1` **in addition**
to the Scala binary suffix `_2.13` etc.
Note: Explicit JVM dependencies will now require `.platform(Platform.jvm)`.
See https://eed3si9n.com/simplifying-sbt-with-common-settings/
Problem
-------
The behavior of bare settings is confusing in a multi-project build.
This is partly due to the fact that to use `ThisBuild` scoping
the build user needs to be aware of the task implementation,
and know if the task is already defined at project level.
Solution
--------
This changes the interpretation of the baresettings to be common
settings, which works similar to the way `ThisBuild` behaves in sbt 1.x,
but since this would be a simple append at project-level, it should
work for any tasks or settings.
Problem
-------
Since sbt-doge merger `++ <sv> <command1>` has used binary compatibility
as a test to select subproject, but it causes surprising situations like
sbt/sbt#6915, and it blurs the responsibility of YAML file and build
file as the version specified in the version can override the Scala
version test on local laptop.
Solution
--------
This removes the compatibiliy check (backward-only or otherwise),
and require that `<sv>` match one of `crossScalaVersions` using the new
Semantic Version selector pattern.