sbt/notes/0.13.9.markdown

  [@cunei]: https://github.com/cunei
  [@eed3si9n]: https://github.com/eed3si9n
  [@gkossakowski]: https://github.com/gkossakowski
  [@jsuereth]: https://github.com/jsuereth
  [@dwijnand]: http://github.com/dwijnand
  [@ajsquared]: https://github.com/ajsquared
  [@jroper]: https://github.com/jroper
  [@kamilkloch]: https://github.com/kamilkloch
  [@DavidPerezIngeniero]: https://github.com/DavidPerezIngeniero
  [@PanAeon]: https://github.com/PanAeon
  [@asflierl]: http://github.com/asflierl
  [@matthewfarwell]: http://github.com/matthewfarwell

  [1970]: https://github.com/sbt/sbt/pull/1970
  [1960]: https://github.com/sbt/sbt/pull/1960
  [1562]: https://github.com/sbt/sbt/issues/1562
  [1900]: https://github.com/sbt/sbt/issues/1900
  [1940]: https://github.com/sbt/sbt/pull/1940
  [1922]: https://github.com/sbt/sbt/pull/1922
  [1721]: https://github.com/sbt/sbt/issues/1721
  [2014]: https://github.com/sbt/sbt/issues/2014
  [2030]: https://github.com/sbt/sbt/pull/2030
  [1998]: https://github.com/sbt/sbt/issues/1998
  [2000]: https://github.com/sbt/sbt/pull/2000
  [1828]: https://github.com/sbt/sbt/issues/1828
  [1992]: https://github.com/sbt/sbt/pull/1992
  [1961]: https://github.com/sbt/sbt/issues/1961
  [1223]: https://github.com/sbt/sbt/issues/1223
  [1773]: https://github.com/sbt/sbt/pull/1773
  [2028]: https://github.com/sbt/sbt/issues/2028
  [1651]: https://github.com/sbt/sbt/issues/1651
  [1990]: https://github.com/sbt/sbt/pull/1990
  [1847]: https://github.com/sbt/sbt/issues/1847
  [1989]: https://github.com/sbt/sbt/pull/1989
  [1856]: https://github.com/sbt/sbt/issues/1856
  [1877]: https://github.com/sbt/sbt/issues/1877
  [2035]: https://github.com/sbt/sbt/pull/2035

### Fixes with compatibility implications

- Starting 0.13.9, `crossScalaVersions` default value is fixed back to the older 0.12.x behavior. See below for
  details
- Starting with 0.13.9, the generated POM files no longer include dependencies on source or javadoc jars obtained via `withSources()` or `withJavadoc()`. See below for details

### Improvements

- Add `-=` and `--=` for settings and tasks, which are the opposites of `+=` and `++=`. [#1922][1922] by [@dwijnand][@dwijnand]
- Add `inThisBuild`, similar to `inConfig`, to allow specifying multiple settings in `ThisBuild` scope. [#1847][1847]/[#1989][1989] by [@dwijnand][@dwijnand]
- Add a nicer toString to SimpleCommand to make it more human-friendly. [#1998][1998]/[#2000][2000] by [@dwijnand][@dwijnand]
- Adds `retrieveManagedSync` key that, when set to true, enables synchronizing retrieved to the current build by removed unneeded files. By [@ajsquared][@ajsquared]
- Adds `configurationsToRetrieve` key, that takes values of `Option[Set[Configuration]]`. If set, when retrieveManaged is true only artifacts in the specified configurations will be retrieved to the current build. By [@ajsquared][@ajsquared]
- Adds `forceUpdatePeriod` key, that takes values of `Option[FiniteDuration]`.  If set, a full `update` will occur after that amount of time without needing to explicitly run the `update` task. By [@ajsquared][@ajsquared]
- Update `ForkError.getMessage()` to include exception's original name. [#2028][2028] by [@kamilkloch][@kamilkloch]
- Add help message for `inspect actual`. [#1651][1651]/[#1990][1990] by [@dwijnand][@dwijnand]
- Support excluding tests in `testOnly`/`testQuick` with `-`, for example `-MySpec`.
  [#1970][1970] by [@matthewfarwell][@matthewfarwell]

### Bug fixes

- Fixes memory/performance issue with cached resolution. See below.
- Correct incremental compile debug message for invalidated products [#1961][1961] by [@jroper][@jroper]
- Enable forced GC by default. See below. 
- Captures errors on `help` command. [#1900][1900]/[#1940][1940] by [@DavidPerezIngeniero][@DavidPerezIngeniero]
- Prevent history command(s) from going into an infinite loop [#1562][1562] by [@PanAeon][@PanAeon]
- Honor overwrite flag when publishing locally. [#1960][1960] by [@asflierl][@asflierl]
- Fixes a certain class of pom corruption that can occur in the presence of parent-poms. [#1856][1856] by [@jsuereth][@jsuereth]
- Add dependency-level exclusions in the POM for project-level exclusions. [#1877][1877]/[#2035][2035] by [@dwijnand][@dwijnand]

### `crossScalaVersions` default value

As of this fix `crossScalaVersions` returns to the behaviour present in `0.12.4` whereby it defaults to what
`scalaVersion` is set to, for example if `scalaVersion` is set to `"2.11.6"`, `crossScalaVersions` now defaults
to `Seq("2.11.6")`.

Therefore when upgrading from any version between `0.13.0` and `0.13.8` be aware of this new default if
your build setup depended on it.

[#1828][1828]/[#1992][1992] by [@dwijnand][@dwijnand]

### POM files no longer include certain source and javadoc jars

When declaring library dependencies using the withSources() or withJavadoc() options, sbt was also including
in the pom file, as dependencies, the source or javadoc jars using the default Maven scope. Such dependencies
might be erroneously processed as they were regular jars by automated tools

[#2001][2001]/[#2027][2027] by [@cunei][@cunei]

### Cached resolution fixes

On a larger dependency graph, the JSON file growing to be 100MB+
with 97% of taken up by *caller* information.
The caller information is not useful once the graph is successfully resolved.
To make the matter worse, these large JSON files were never cleaned up.

sbt 0.13.9 creates a single caller to represent all callers,
which fixes `OutOfMemoryException` seen on some builds.
This generally shrinks the size of JSON, so it should make the IO operations faster.
Dynamic graphs will be rotated with directories named after `yyyy-mm-dd`,
and stale JSON files will be cleaned up after few days.

[#2030][2030]/[#1721][1721]/[#2014][2014] by [@eed3si9n][@eed3si9n]

### Force GC

[@cunei][@cunei] in [#1223][1223] discovered that sbt leaks PermGen
when it creates classloaders to call Scala Compilers.
sbt 0.13.9 will call GC on a set interval (default: 60s).
It will also call GC right before cross building.
This behavior can diabled using by setting false to `forcegc`
setting or `sbt.task.forcegc` flag.

[#1773][1773] by [@eed3si9n][@eed3si9n]