Add swoval java formatting plugin

The swoval javafmt plugin uses the google java formatter (which I
believe is the only widely used java formatter) to format source files.
It does not provide an automatic javafmtOnCompile method like the
scalafmt plugin so I had to manually implement that functionality. In
general the java formatter is much faster than scalafmt so the impact of
having javafmtOnCompile set to true is very low.

.travis.yml

@@ -11,7 +11,7 @@ env:
     # WHITESOURCE_PASSWORD=
     - secure: d3bu2KNwsVHwfhbGgO+gmRfDKBJhfICdCJFGWKf2w3Gv86AJZX9nuTYRxz0KtdvEHO5Xw8WTBZLPb2thSJqhw9OCm4J8TBAVqCP0ruUj4+aqBUFy4bVexQ6WKE6nWHs4JPzPk8c6uC1LG3hMuzlC8RGETXtL/n81Ef1u7NjyXjs=
   matrix:
-    - SBT_CMD="mimaReportBinaryIssues ;scalafmtCheckAll ; scalafmtSbtCheck; headerCheck ;test:headerCheck ;whitesourceOnPush ;test:compile; publishLocal ;mainSettingsProj/test ;safeUnitTests ;otherUnitTests; doc; $UTIL_TESTS; ++$SCALA_213; $UTIL_TESTS"
+    - SBT_CMD="mimaReportBinaryIssues ; javafmtCheck ; Test / javafmtCheck; scalafmtCheckAll ; scalafmtSbtCheck; headerCheck ;test:headerCheck ;whitesourceOnPush ;test:compile; publishLocal ;mainSettingsProj/test ;safeUnitTests ;otherUnitTests; doc; $UTIL_TESTS; ++$SCALA_213; $UTIL_TESTS"
     - SBT_CMD="scripted actions/* apiinfo/* compiler-project/* ivy-deps-management/* reporter/* tests/* watch/* classloader-cache/* package/*"
     - SBT_CMD="scripted dependency-management/* plugins/* project-load/* java/* run/* nio/*"
     - SBT_CMD="repoOverrideTest:scripted dependency-management/*; scripted source-dependencies/* project/*"

build.sbt

@@ -87,6 +87,16 @@ def commonBaseSettings: Seq[Setting[_]] = Def.settings(
       s"https://github.com/sbt/sbt/tree/$tagOrSha€{FILE_PATH}.scala"
     )
   },
+  Compile / javafmtOnCompile := Def
+    .taskDyn(if ((scalafmtOnCompile).value) Compile / javafmt else Def.task(()))
+    .value,
+  Test / javafmtOnCompile := Def
+    .taskDyn(if ((Test / scalafmtOnCompile).value) Test / javafmt else Def.task(()))
+    .value,
+  Compile / unmanagedSources / inputFileStamps :=
+    (Compile / unmanagedSources / inputFileStamps).dependsOn(Compile / javafmtOnCompile).value,
+  Test / unmanagedSources / inputFileStamps :=
+    (Test / unmanagedSources / inputFileStamps).dependsOn(Test / javafmtOnCompile).value,
   crossScalaVersions := Seq(baseScalaVersion),
   bintrayPackage := (bintrayPackage in ThisBuild).value,
   bintrayRepository := (bintrayRepository in ThisBuild).value,
@@ -1257,6 +1267,7 @@ lazy val otherProjects: ScopeFilter = ScopeFilter(
   ),
   inConfigurations(Test)
 )
+lazy val javafmtOnCompile = taskKey[Unit]("Formats java sources before compile")
 
 def customCommands: Seq[Setting[_]] = Seq(
   commands += Command.command("setupBuildScala212") { state =>

project/plugins.sbt

@@ -10,3 +10,4 @@ addSbtPlugin("com.eed3si9n" % "sbt-buildinfo" % "0.9.0")
 addSbtPlugin("com.lightbend" % "sbt-whitesource" % "0.1.14")
 addSbtPlugin("com.eed3si9n" % "sbt-assembly" % "0.14.9")
 addSbtPlugin("com.typesafe" % "sbt-mima-plugin" % "0.6.1")
+addSbtPlugin("com.swoval" % "sbt-java-format" % "0.2.3")