diff --git a/.drone.yml b/.drone.yml
index b3dacd40ec..af78d053fb 100644
--- a/.drone.yml
+++ b/.drone.yml
@@ -2,9 +2,24 @@ build:
   image: olafurpg/scalafix:0.0.1
   commands:
     - export JVM_OPTS="-Xms4000m -Xmx55g -XX:MaxPermSize=2000m -Xss4m -XX:ReservedCodeCacheSize=1024m -XX:+TieredCompilation -XX:+CMSClassUnloadingEnabled -XX:+UseConcMarkSweepGC"
-    - pip install --user codecov
+    # configuring ivy.home doesn't seem to work. Maybe related:
+    #   https://github.com/sbt/sbt/issues/1894
+    # After 10+ experiments I've given up on trying to use sbt.ivy.yhome and
+    # copy the files myself instead, as recommended here:
+    #   http://readme.drone.io/usage/caching/
+    - test -d /drone/.sbt && cp -a /drone/.sbt /root
+    - rm -rf /drone/.sbt
+
+    - test -d /drone/.ivy2 && cp -a /drone/.ivy2 /root
+    - rm -rf /drone/.ivy2
+
     - ./bin/testAll.sh
-    # I can't be bothered to hide this token.
-#    - $HOME/.local/bin/codecov -t 5f2117aa-0a01-4cf1-8bf7-631a62ccb47a
 
+    - cp -a /root/.ivy2 /drone
+    - cp -a /root/.sbt /drone
+cache:
+  mount:
+    - /drone/.sbt
+    - /drone/.ivy2
+    - /drone/cache
 
diff --git a/.travis.yml b/.travis.yml
index acce917c62..32893baaa5 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -9,13 +9,8 @@ git:
   submodules: false
 scala:
 - 2.11.8
-before_install:
-- pip install --user codecov
 script:
 - "./bin/testAll.sh"
-#after_success:
-#- "./bin/travisPublish.sh"
-#- codecov
 notifications:
   email:
   - olafurpg@gmail.com
diff --git a/bin/publish.sh b/bin/publish.sh
index a33ceeeb17..0f4c3dc191 100755
--- a/bin/publish.sh
+++ b/bin/publish.sh
@@ -1,7 +1,7 @@
 #!/bin/bash
 set -e
 
-version=$(sed -n -e 's/.*val nightly = "\(.*\)"/\1/p' core/src/main/scala/org/scalafmt/Versions.scala)
+version=$(sed -n -e 's/.*val nightly = "\(.*\)"/\1/p' core/target/scala-2.11/src_managed/main/sbt-buildinfo/Versions.scala)
 tag="v${version}"
 tarfile="cli/target/scalafmt.tar.gz"
 current_branch=$(git rev-parse --abbrev-ref HEAD)
diff --git a/bin/sonatypePublish.sh b/bin/sonatypePublish.sh
index f9744d5556..def2758107 100644
--- a/bin/sonatypePublish.sh
+++ b/bin/sonatypePublish.sh
@@ -2,7 +2,7 @@ set -e
 if [ $TRAVIS_SECURE_ENV_VARS = "true" ]; then
   echo "Publishing snapshot..."
   # Assert that nighly is set to snapshot
-  grep "nightly.*SNAPSHOT" core/src/main/scala/org/scalafmt/Versions.scala
+  grep "nightly.*SNAPSHOT" core/target/scala-2.11/src_managed/main/sbt-buildinfo/Versions.scala
   sbt publishSigned
 else
   echo "Skipping publish"
diff --git a/bin/testAll.sh b/bin/testAll.sh
index 0f17bbf790..2bb1c2650e 100755
--- a/bin/testAll.sh
+++ b/bin/testAll.sh
@@ -1,9 +1,7 @@
 #!/bin/bash
 set -e
 
-#sbt clean coverage test
 sbt clean test
 sbt "core/test:runMain org.scalafmt.FormatExperimentApp"
-./bin/issue492.sh
-#sbt coverageAggregate
+sbt "; publishLocal ; scripted"
 
diff --git a/bin/travisPublish.sh b/bin/travisPublish.sh
index c327152268..62e3349c3e 100755
--- a/bin/travisPublish.sh
+++ b/bin/travisPublish.sh
@@ -16,7 +16,7 @@ if [[ ${TRAVIS_SECURE_ENV_VARS} == "true" && ${TRAVIS_BRANCH} == "master" ]]; th
   echo "Publishing snapshot..."
   setupDeployKey
   # only publish if nightly is a snapshot.
-  if grep "nightly.*SNAPSHOT" core/src/main/scala/org/scalafmt/Versions.scala; then
+  if grep "nightly.*SNAPSHOT" core/target/scala-2.11/src_managed/main/sbt-buildinfo/Versions.scala; then
     echo "Publishing snapshot"
     sbt publish # snapshot
   else
diff --git a/build.sbt b/build.sbt
index 58b92c356c..203da8d047 100644
--- a/build.sbt
+++ b/build.sbt
@@ -1,10 +1,11 @@
 import scoverage.ScoverageSbtPlugin.ScoverageKeys.coverageHighlighting
 
+// The version number used in docs.
+def latestStableVersion: String = "0.4.10"
 lazy val buildSettings = Seq(
   organization := "com.geirsson",
-  // See core/src/main/scala/org/scalafmt/Versions.scala
-  version := org.scalafmt.Versions.nightly,
-  scalaVersion := org.scalafmt.Versions.scala,
+  version := "0.4.10-SNAPSHOT",
+  scalaVersion := "2.11.8",
   updateOptions := updateOptions.value.withCachedResolution(true)
 )
 
@@ -86,6 +87,20 @@ lazy val noPublish = Seq(
   publishLocal := {}
 )
 
+lazy val buildInfoSettings: Seq[Def.Setting[_]] = Seq(
+  buildInfoKeys := Seq[BuildInfoKey](
+    name,
+    version,
+    "nightly" -> version.value,
+    "stable" -> latestStableVersion,
+    "scala" -> scalaVersion.value,
+    scalaVersion,
+    sbtVersion
+  ),
+  buildInfoPackage := "org.scalafmt",
+  buildInfoObject := "Versions"
+)
+
 lazy val allSettings = commonSettings ++ buildSettings ++ publishSettings
 
 lazy val root = project
@@ -108,14 +123,16 @@ lazy val root = project
     utils,
     core,
     metaconfig,
-    readme
+    readme,
+    scalafmtSbt
   )
   .dependsOn(core)
 
 lazy val core = project
-  .settings(allSettings)
   .settings(
+    allSettings,
     metaMacroSettings,
+    buildInfoSettings,
     moduleName := "scalafmt-core",
     libraryDependencies ++= Seq(
       "com.lihaoyi"    %% "sourcecode"   % "0.1.2",
@@ -135,6 +152,7 @@ lazy val core = project
       "org.scalamacros" % "paradise" % "2.1.0" cross CrossVersion.full)
   )
   .dependsOn(metaconfig, utils)
+  .enablePlugins(BuildInfoPlugin)
 
 lazy val cliJvmOptions = Seq(
   "-Xss4m"
@@ -161,10 +179,9 @@ lazy val cli = project
 lazy val bootstrap = project
   .settings(
     allSettings,
+    buildInfoSettings,
     //  crossScalaVersions := Seq("2.10.6", "2.11.8"),
     moduleName := "scalafmt-bootstrap",
-    sources in Compile +=
-      baseDirectory.value / "../core/src/main/scala/org/scalafmt/Versions.scala",
     libraryDependencies ++= Seq(
       "com.martiansoftware" % "nailgun-server"  % "0.9.1",
       "io.get-coursier"     %% "coursier"       % "1.0.0-M14",
@@ -173,6 +190,36 @@ lazy val bootstrap = project
     )
   )
   .dependsOn(utils)
+  .enablePlugins(BuildInfoPlugin)
+
+lazy val scalafmtSbt = project
+  .settings(
+    allSettings,
+    buildInfoSettings,
+    ScriptedPlugin.scriptedSettings,
+    scripted := scripted
+      .dependsOn(
+        publishLocal in cli,
+        publishLocal in core,
+        publishLocal in metaconfig,
+        publishLocal in utils
+      )
+      .evaluated,
+    sbtPlugin := true,
+    coverageHighlighting := false,
+    scalaVersion := "2.10.5",
+    // In convention of sbt plugins, the module is sbt-scalafmt instead of scalafmt-sbt.
+    moduleName := "sbt-scalafmt",
+    scriptedLaunchOpts := Seq(
+      "-Dplugin.version=" + version.value,
+      // .jvmopts is ignored, simulate here
+      "-XX:MaxPermSize=256m",
+      "-Xmx2g",
+      "-Xss2m"
+    ),
+    scriptedBufferLog := false
+  )
+  .enablePlugins(BuildInfoPlugin)
 
 lazy val benchmarks = project
   .settings(moduleName := "scalafmt-benchmarks")
diff --git a/cli/src/main/scala/org/scalafmt/cli/Cli.scala b/cli/src/main/scala/org/scalafmt/cli/Cli.scala
index 66a5c2704a..3e1faacded 100644
--- a/cli/src/main/scala/org/scalafmt/cli/Cli.scala
+++ b/cli/src/main/scala/org/scalafmt/cli/Cli.scala
@@ -19,7 +19,9 @@ import org.scalafmt.config.ScalafmtConfig
 import org.scalafmt.util.FileOps
 import org.scalafmt.util.LogLevel
 import com.martiansoftware.nailgun.NGContext
+import org.scalafmt.config.FilterMatcher
 import org.scalafmt.util.AbsoluteFile
+import org.scalafmt.util.logger
 
 object Cli {
   def nailMain(nGContext: NGContext): Unit = {
@@ -77,13 +79,6 @@ object Cli {
     CliArgParser.scoptParser.parse(args, init).map(CliOptions.auto(init))
   }
 
-  private def mkRegexp(filters: Seq[String]): Regex =
-    filters match {
-      case Nil => "$a".r // will never match anything
-      case head :: Nil => head.r
-      case _ => filters.mkString("(", "|", ")").r
-    }
-
   def canFormat(path: AbsoluteFile): Boolean =
     canFormat(path.path)
 
@@ -102,22 +97,20 @@ object Cli {
 
   /** Returns file paths defined via options.{customFiles,customExclude} */
   def getFilesFromCliOptions(options: CliOptions): Seq[AbsoluteFile] = {
-    val exclude = mkRegexp(options.customExcludes)
+    val exclude = FilterMatcher.mkRegexp(options.customExcludes)
     expandCustomFiles(options.common.workingDirectory, options.customFiles)
       .filter(x => exclude.findFirstIn(x.path).isEmpty)
   }
 
+  private def getFilesFromDiff(options: CliOptions): Seq[AbsoluteFile] = {
+    val branch = options.diff.get
+    options.gitOps.diff(branch).filter(options.config.project.matcher.matches)
+  }
+
   /** Returns file paths defined via options.project */
   private def getFilesFromProject(options: CliOptions): Seq[AbsoluteFile] = {
     val project = options.config.project
-    val include = mkRegexp(project.includeFilters)
-    val exclude = mkRegexp(project.excludeFilters)
-
-    def matches(file: AbsoluteFile): Boolean = {
-      val path = file.path
-      include.findFirstIn(path).isDefined &&
-      exclude.findFirstIn(path).isEmpty
-    }
+    val matcher = project.matcher
     val projectFiles: Seq[AbsoluteFile] = (
       if (project.git) {
         options.gitOps.lsTree
@@ -130,7 +123,7 @@ object Cli {
         options.common.workingDirectory,
         AbsoluteFile.fromFiles(project.files.map(new File(_)),
                                options.common.workingDirectory))
-    (customFiles ++ projectFiles).filter(matches)
+    (customFiles ++ projectFiles).filter(matcher.matches)
   }
 
   private def getInputMethods(options: CliOptions): Seq[InputMethod] = {
@@ -139,6 +132,7 @@ object Cli {
     } else {
       val projectFiles: Seq[AbsoluteFile] =
         if (options.customFiles.nonEmpty) getFilesFromCliOptions(options)
+        else if (options.diff.isDefined) getFilesFromDiff(options)
         else getFilesFromProject(options)
       projectFiles.map(InputMethod.FileContents.apply)
     }
diff --git a/cli/src/main/scala/org/scalafmt/cli/CliArgParser.scala b/cli/src/main/scala/org/scalafmt/cli/CliArgParser.scala
index 6f958084cb..53bea76ee8 100644
--- a/cli/src/main/scala/org/scalafmt/cli/CliArgParser.scala
+++ b/cli/src/main/scala/org/scalafmt/cli/CliArgParser.scala
@@ -18,19 +18,23 @@ object CliArgParser {
   @GitCommit val gitCommit: String = ???
   @BuildTime val buildTimeMs: Long = ???
 
-  val usageExamples =
+  val usageExamples: String =
     """|scalafmt  # Format all files in the current project, with config determined:
        |          # 1. .scalafmt.conf inside root directory of current git repo
-       |          #    IF the following setting is enabled: project.git = true
        |          # 2. .scalafmt.conf file in current directory
        |          # 3. default style
        |          # from .scalafmt.conf in the root directory, if the file exists.
        |scalafmt --test # same as without --test, except
        |                # 1. throws an exception on the first mis-formatted file
        |                # 2. does not write to any files.
+       |scalafmt --diff        # same as without --diff, except only format files
+       |                       # in git diff against master branch.
+       |scalafmt --diff --test # same as --test, except only for edited files
+       |                       # in git diff against master branch.
+       |scalafmt --diff-branch 2.x        # same as --diff, except against branch 2.x
+       |scalafmt --diff-branch 2.x --test # same as --diff
        |scalafmt --stdin                           # read from stdin and print to stdout
        |scalafmt --stdin --assume-filename foo.sbt # required to format .sbt files
-       |
        |scalafmt -f Code.scala             # print formatted contents to stdout.
        |scalafmt -i -f Code1.scala,A.scala # write formatted contents to file.
        |scalafmt -i -f . --exclude target  # format all files in directory excluding target
@@ -101,6 +105,12 @@ object CliArgParser {
           c.copy(migrate =
             Some(AbsoluteFile.fromFile(file, c.common.workingDirectory))))
         .text("""migrate .scalafmt CLI style configuration to hocon style configuration in .scalafmt.conf""")
+      opt[Unit]("diff")
+        .action((_, c) => c.copy(diff = Some("master")))
+        .text("If set, only format edited files in git diff against master.")
+      opt[String]("diff-branch")
+        .action((branch, c) => c.copy(diff = Some(branch)))
+        .text("If set, only format edited files in git diff against provided branch.")
       opt[Unit]("build-info")
         .action({
           case (_, c) =>
diff --git a/cli/src/main/scala/org/scalafmt/cli/CliOptions.scala b/cli/src/main/scala/org/scalafmt/cli/CliOptions.scala
index 0ed85b97a8..33a8cbce23 100644
--- a/cli/src/main/scala/org/scalafmt/cli/CliOptions.scala
+++ b/cli/src/main/scala/org/scalafmt/cli/CliOptions.scala
@@ -33,7 +33,7 @@ object CliOptions {
     val style: Option[ScalafmtConfig] = if (init.config != parsed.config) {
       Option(parsed.config)
     } else {
-      tryGit(parsed).orElse(tryCurrentDirectory(parsed))
+      tryCurrentDirectory(parsed).orElse(tryGit(parsed))
     }
     val inplace =
       !parsed.testing && (
@@ -61,7 +61,6 @@ object CliOptions {
           case Left(e) => throw e
         }
       }
-      if parsedConfig.project.git
     } yield parsedConfig
   }
 
@@ -89,6 +88,7 @@ case class CliOptions(
     inPlace: Boolean = false,
     testing: Boolean = false,
     stdIn: Boolean = false,
+    diff: Option[String] = None,
     assumeFilename: String = "stdin.scala", // used when read from stdin
     migrate: Option[AbsoluteFile] = None,
     common: CommonOptions = CommonOptions(),
diff --git a/cli/src/main/scala/org/scalafmt/cli/Scalafmt210.scala b/cli/src/main/scala/org/scalafmt/cli/Scalafmt210.scala
index 883e117c3a..71cd057600 100644
--- a/cli/src/main/scala/org/scalafmt/cli/Scalafmt210.scala
+++ b/cli/src/main/scala/org/scalafmt/cli/Scalafmt210.scala
@@ -1,5 +1,7 @@
 package org.scalafmt.cli
 
+import scala.util.matching.Regex
+
 import java.io.File
 
 import org.scalafmt.Error.InvalidScalafmtConfiguration
@@ -15,8 +17,10 @@ import org.scalafmt.util.LoggerOps._
   * plugin.
   */
 class Scalafmt210 {
-  val oldConfig = "--".r
+  val oldConfig: Regex = "--".r
+  def main(args: Array[String]): Unit = Cli.main(args)
 
+  // The rest is for scalafmtIncremental.
   def format(code: String, configFile: String, filename: String): String = {
     StyleCache.getStyleForFileOrError(configFile) match {
       case Left(throwable) => {
diff --git a/cli/src/test/scala/org/scalafmt/cli/CliTest.scala b/cli/src/test/scala/org/scalafmt/cli/CliTest.scala
index 8a5492776d..c2768d6178 100644
--- a/cli/src/test/scala/org/scalafmt/cli/CliTest.scala
+++ b/cli/src/test/scala/org/scalafmt/cli/CliTest.scala
@@ -261,13 +261,15 @@ class CliTest extends FunSuite with DiffAssertions {
          |object A   { }
          |""".stripMargin
 
-    val init: CliOptions = getMockOptions(input)
-    val config = Cli.getConfig(Array.empty[String], init).get
-    Cli.run(config)
-    val obtained = dir2string(input)
-    assertNoDiff(obtained, expected)
-    val configTest = Cli.getConfig(Array("--test"), init).get
-    Cli.run(configTest)
+    Seq(Array.empty[String], Array("--diff")).foreach { args =>
+      val init: CliOptions = getMockOptions(input)
+      val config = Cli.getConfig(args, init).get
+      Cli.run(config)
+      val obtained = dir2string(input)
+      assertNoDiff(obtained, expected)
+      val configTest = Cli.getConfig(Array("--test"), init).get
+      Cli.run(configTest)
+    }
   }
 
   test("config is read even from nested dir") {
diff --git a/cli/src/test/scala/org/scalafmt/cli/FakeGitOps.scala b/cli/src/test/scala/org/scalafmt/cli/FakeGitOps.scala
index 8deff2eb8b..f20eeaeece 100644
--- a/cli/src/test/scala/org/scalafmt/cli/FakeGitOps.scala
+++ b/cli/src/test/scala/org/scalafmt/cli/FakeGitOps.scala
@@ -10,4 +10,5 @@ import org.scalafmt.util.logger
 class FakeGitOps(root: AbsoluteFile) extends GitOps {
   override def lsTree: Vector[AbsoluteFile] = FileOps.listFiles(root)
   override def rootDir: Option[AbsoluteFile] = Some(root)
+  override def diff(branch: String): Seq[AbsoluteFile] = lsTree
 }
diff --git a/core/src/main/scala/org/scalafmt/Versions.scala b/core/src/main/scala/org/scalafmt/Versions.scala
deleted file mode 100644
index 75b45d95d5..0000000000
--- a/core/src/main/scala/org/scalafmt/Versions.scala
+++ /dev/null
@@ -1,12 +0,0 @@
-package org.scalafmt
-
-/**
-  * Single source of truth for version number.
-  */
-object Versions {
-  // Nightly, used in CLI, build.sbt, etc.
-  val nightly = "0.4.10"
-  // Stable, used in official user docs.
-  val stable = "0.4.10"
-  val scala = "2.11.8"
-}
diff --git a/core/src/main/scala/org/scalafmt/config/FilterMatcher.scala b/core/src/main/scala/org/scalafmt/config/FilterMatcher.scala
new file mode 100644
index 0000000000..d75ee30e95
--- /dev/null
+++ b/core/src/main/scala/org/scalafmt/config/FilterMatcher.scala
@@ -0,0 +1,26 @@
+package org.scalafmt.config
+
+import scala.util.matching.Regex
+
+import org.scalafmt.util.AbsoluteFile
+
+case class FilterMatcher(include: Regex, exclude: Regex) {
+  def matches(file: AbsoluteFile): Boolean = matches(file.path)
+  def matches(input: String): Boolean =
+    include.findFirstIn(input).isDefined &&
+      exclude.findFirstIn(input).isEmpty
+}
+
+object FilterMatcher {
+  val matchEverything = new FilterMatcher(".*".r, mkRegexp(Nil))
+
+  def mkRegexp(filters: Seq[String]): Regex =
+    filters match {
+      case Nil => "$a".r // will never match anything
+      case head :: Nil => head.r
+      case _ => filters.mkString("(", "|", ")").r
+    }
+
+  def apply(includes: Seq[String], excludes: Seq[String]): FilterMatcher =
+    new FilterMatcher(mkRegexp(includes), mkRegexp(excludes))
+}
diff --git a/core/src/main/scala/org/scalafmt/config/ProjectFiles.scala b/core/src/main/scala/org/scalafmt/config/ProjectFiles.scala
index 95ec72d05d..771efde4a2 100644
--- a/core/src/main/scala/org/scalafmt/config/ProjectFiles.scala
+++ b/core/src/main/scala/org/scalafmt/config/ProjectFiles.scala
@@ -1,13 +1,14 @@
 package org.scalafmt.config
 
-import scala.util.matching.Regex
-
 import metaconfig.ConfigReader
 
 @ConfigReader
 case class ProjectFiles(
     git: Boolean = false,
     files: Seq[String] = Nil,
-    includeFilters: Seq[String] = Seq(".*"),
+    includeFilters: Seq[String] = Seq(".*\\.scala", ".*\\.sbt"),
     excludeFilters: Seq[String] = Nil
-)
+) {
+  lazy val matcher: FilterMatcher =
+    FilterMatcher(includeFilters, excludeFilters)
+}
diff --git a/project/build.sbt b/project/build.sbt
deleted file mode 100644
index d560b26642..0000000000
--- a/project/build.sbt
+++ /dev/null
@@ -1,3 +0,0 @@
-sources in Compile += {
-  baseDirectory.value / "../core/src/main/scala/org/scalafmt/Versions.scala"
-}
diff --git a/project/plugins.sbt b/project/plugins.sbt
index f0624ff071..7b9091b89e 100644
--- a/project/plugins.sbt
+++ b/project/plugins.sbt
@@ -1,21 +1,13 @@
 resolvers += Classpaths.sbtPluginReleases
-resolvers += Resolver.url(
-  "dancingrobot84-bintray",
-  url("http://dl.bintray.com/dancingrobot84/sbt-plugins/")
-)(Resolver.ivyStylePatterns)
-
-// I would love to enable this plugin but it one point I had disabled almost all
-// of the warts.
-// addSbtPlugin("org.wartremover"    % "sbt-wartremover"     % "1.1.1")
 
+addSbtPlugin("com.eed3si9n"       % "sbt-buildinfo"       % "0.6.1")
 addSbtPlugin("io.get-coursier"    % "sbt-coursier"        % "1.0.0-M14")
 addSbtPlugin("com.eed3si9n"       % "sbt-assembly"        % "0.14.3")
-addSbtPlugin("org.scoverage"      % "sbt-scoverage"       % "1.0.1")
 addSbtPlugin("pl.project13.scala" % "sbt-jmh"             % "0.2.15")
 addSbtPlugin("com.lihaoyi"        % "scalatex-sbt-plugin" % "0.3.5")
 addSbtPlugin("org.xerial.sbt"     % "sbt-sonatype"        % "1.1")
 addSbtPlugin("com.jsuereth"       % "sbt-pgp"             % "1.0.0")
-addSbtPlugin("com.dancingrobot84" % "sbt-idea-plugin"     % "0.4.2")
 addSbtPlugin("org.xerial.sbt"     % "sbt-pack"            % "0.8.0")
+addSbtPlugin("org.scoverage"      % "sbt-scoverage"       % "1.0.1")
 
 libraryDependencies += "org.scala-sbt" % "scripted-plugin" % sbtVersion.value
diff --git a/readme/Installation.scalatex b/readme/Installation.scalatex
index 81f6dcb43b..d594d44a90 100644
--- a/readme/Installation.scalatex
+++ b/readme/Installation.scalatex
@@ -155,6 +155,64 @@
         org.scalafmt.cli.CliArgParser.buildInfo + "\n" +
         org.scalafmt.cli.CliArgParser.scoptParser.usage)
 
+  @sect{SBT}
+    @p
+      @note. If you rely on the SBT plugin, please consider becoming a maintainer!
+    @p
+      The sbt plugin is just a thin wrapper around the command line interface.
+
+    @hl.scala
+      addSbtPlugin("com.geirsson" % "sbt-scalafmt" % "@org.scalafmt.Versions.stable")
+
+    @ul
+      @li
+        @lnk("Here is an example repository using sbt plugin.",
+             "https://github.com/olafurpg/sbt-scalafmt-example")
+      @li
+        Run @code("sbt scalafmt") to format all files in the project.
+        You can add pass any command line flags to @code{scalafmt}.
+        See @sect.ref{--help} for more details.
+        Example,
+        @hl.scala
+          sbt "scalafmt --help"
+          scalafmt x.y.z
+          Usage: ...
+      @li
+        There are three handy aliases for the @code{scalafmt} command.
+        @ul
+          @li
+            @code{scalafmtTest -> scalafmt --test}
+          @li
+            @code{scalafmtDiff -> scalafmt --diff}
+          @li
+            @code{scalafmtDiffTest -> scalafmt --diff --test}
+      @li
+        The plugin will automatically pick up your @sect.ref{Configuration} in
+        @code{.scalafmt.conf}.
+        @p
+          The configuration must be defined in .scalafmt.conf in the root directory
+          of your project. Why? Because integrations like IntelliJ rely on the
+          file existing there.
+        @p
+          If you want to define the configuration somehow differently, you can
+          use some trick like this in @code{build.sbt} or from within an
+          sbt plugin settings
+
+          @hl.scala
+            // define setting key to write configuration to .scalafmt.conf
+            SettingKey[Unit]("scalafmtGenerateConfig") :=
+              IO.write( // writes to file once when build is loaded
+                file(".scalafmt.conf"),
+                """style = IntelliJ
+                  |# Your configuration here
+                  """.stripMargin.getBytes("UTF-8")
+              )
+      @p
+        There is no setting to reformat on compile, please consider contributing it
+        if you would like to use that feature!
+        Until then, I encourage you to find another way to incorporate scalafmt
+        into your workflow.
+
   @sect{Vim}
     @ul
       @li
diff --git a/scalafmtSbt/src/main/scala/org/scalafmt/sbt/ScalafmtPlugin.scala b/scalafmtSbt/src/main/scala/org/scalafmt/sbt/ScalafmtPlugin.scala
new file mode 100644
index 0000000000..de7e898019
--- /dev/null
+++ b/scalafmtSbt/src/main/scala/org/scalafmt/sbt/ScalafmtPlugin.scala
@@ -0,0 +1,54 @@
+package org.scalafmt.sbt
+
+import sbt.Keys._
+import sbt._
+import sbt.plugins.JvmPlugin
+
+object ScalafmtPlugin extends AutoPlugin {
+  private def baseCmd = "scalafmt-stub/runMain org.scalafmt.cli.Cli "
+  private def cmd(args: String*)(s: State): State =
+    s"$baseCmd ${args.mkString(" ")}" :: s
+  object autoImport {
+
+    lazy val scalafmt: Command =
+      Command.args("scalafmt", "run the scalafmt command line interface.") {
+        case (s, args) => s"$baseCmd ${args.mkString(" ")}" :: s
+      }
+    // These are not strictly necessary, since they can be run with the
+    // scalafmt command. However, they're convenient to avoid the need for
+    // parentheses when running `sbt "scalafmt --test"`.
+    lazy val scalafmtTest: Command =
+      Command.command("scalafmtTest")(cmd("--test"))
+    lazy val scalafmtDiff: Command =
+      Command.command("scalafmtDiff")(cmd("--diff"))
+    lazy val scalafmtDiffTest: Command =
+      Command.command("scalafmtDiffTest")(cmd("--diff", "--test"))
+  }
+  import autoImport._
+  lazy val scalafmtStub: Project = Project(
+    id = "scalafmt-stub",
+    base = file("project/scalafmt")
+  ).settings(
+    scalaVersion := "2.11.8",
+    libraryDependencies +=
+      "com.geirsson" %% "scalafmt-cli" % _root_.org.scalafmt.Versions.nightly
+  )
+  override def globalSettings: Seq[Def.Setting[_]] = Seq(
+    commands ++= {
+      if (sbtVersion.value < "0.13.13") {
+        // can't do streams.value.log.warn since streams is a task and
+        // settings like `commands` can't depend on tasks.
+        val warn = s"[${scala.Console.YELLOW}warn${scala.Console.RESET}]"
+        System.err.println(
+          s"$warn sbt-scalafmt requires sbt.version=0.13.13 or higher. " +
+            s"Please upgrade sbt to expose the `scalafmt` command.")
+        Nil
+      } else {
+        Seq(scalafmt, scalafmtTest, scalafmtDiff, scalafmtDiffTest)
+      }
+    }
+  )
+  override def extraProjects: Seq[Project] = Seq(scalafmtStub)
+  override def trigger: PluginTrigger = allRequirements
+  override def requires = JvmPlugin
+}
diff --git a/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/.gitignore b/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/.gitignore
new file mode 100644
index 0000000000..0064e95172
--- /dev/null
+++ b/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/.gitignore
@@ -0,0 +1,23 @@
+*.class
+*.log
+
+# sbt specific
+.cache
+.history
+.lib/
+dist/*
+target/
+lib_managed/
+src_managed/
+project/boot/
+project/plugins/project/
+
+# Scala-IDE specific
+.scala_dependencies
+.worksheet
+
+.idea
+
+# ENSIME specific
+.ensime_cache/
+.ensime
diff --git a/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/.scalafmt.conf b/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/.scalafmt.conf
new file mode 100644
index 0000000000..9e75a6c9f5
--- /dev/null
+++ b/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/.scalafmt.conf
@@ -0,0 +1,4 @@
+style = IntelliJ
+project.excludeFilters = [
+  target/
+]
diff --git a/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/build.sbt b/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/build.sbt
new file mode 100644
index 0000000000..f2c022cc20
--- /dev/null
+++ b/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/build.sbt
@@ -0,0 +1,68 @@
+import java.io.File
+
+lazy val root = project
+  .in(file("."))
+  .aggregate(
+    p1,
+    p2,
+    p3
+  )
+
+lazy val p1 = project.settings(scalaVersion := "2.10.5")
+lazy val p2 = project.settings(scalaVersion := "2.11.8")
+lazy val p3 = project.settings(scalaVersion := "2.12.1")
+
+def assertContentsEqual(file: File, expected: String): Unit = {
+  val obtained =
+    scala.io.Source.fromFile(file).getLines().mkString("\n")
+
+  if (obtained.trim != expected.trim) {
+    val msg =
+      s"""File: $file
+         |Obtained output:
+         |$obtained
+         |Expected:
+         |$expected
+         |""".stripMargin
+    System.err.println(msg)
+    throw new Exception(msg)
+  }
+}
+
+TaskKey[Unit]("setupGitRepo") := {
+  import sys.process._
+  Seq("git", "init").!!
+  Seq("git", "config", "user.email", "a@a.is").!!
+  Seq("git", "config", "user.name", "a").!!
+  Seq("git", "add", ".").!!
+  Seq("git", "commit", "-m", "wip").!!
+}
+
+TaskKey[Unit]("check") := {
+  (1 to 3).foreach { i =>
+    val expected =
+      """
+        |object Test {
+        |  foo(
+        |    a, // comment
+        |    b
+        |  )
+        |}
+        """.stripMargin
+    val expected2 = expected.replaceFirst("Test", "MainTest")
+    assertContentsEqual(file(s"p$i/src/main/scala/Test.scala"), expected)
+    assertContentsEqual(file(s"p$i/src/test/scala/MainTest.scala"), expected2)
+  }
+  assertContentsEqual(
+    new File("project/plugins.sbt"),
+    """
+      |addSbtPlugin(
+      |  "com.geirsson" % "sbt-scalafmt" % System.getProperty("plugin.version")
+      |)
+    """.stripMargin
+  )
+  assertContentsEqual(
+    new File("target/src_managed/Generated.scala"),
+    """object      DontFormatMe   {    println(1)    }"""
+  )
+}
diff --git a/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/p1/src/main/scala/Test.scala b/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/p1/src/main/scala/Test.scala
new file mode 100644
index 0000000000..a96ec3f1fa
--- /dev/null
+++ b/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/p1/src/main/scala/Test.scala
@@ -0,0 +1,6 @@
+object
+Test
+{
+  foo(a, // comment
+    b)
+}
diff --git a/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/p1/src/test/scala/MainTest.scala b/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/p1/src/test/scala/MainTest.scala
new file mode 100644
index 0000000000..7d4e15448b
--- /dev/null
+++ b/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/p1/src/test/scala/MainTest.scala
@@ -0,0 +1,6 @@
+object
+MainTest
+{
+  foo(a, // comment
+    b)
+}
diff --git a/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/p2/src/main/scala/Test.scala b/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/p2/src/main/scala/Test.scala
new file mode 100644
index 0000000000..a96ec3f1fa
--- /dev/null
+++ b/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/p2/src/main/scala/Test.scala
@@ -0,0 +1,6 @@
+object
+Test
+{
+  foo(a, // comment
+    b)
+}
diff --git a/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/p2/src/test/scala/MainTest.scala b/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/p2/src/test/scala/MainTest.scala
new file mode 100644
index 0000000000..7d4e15448b
--- /dev/null
+++ b/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/p2/src/test/scala/MainTest.scala
@@ -0,0 +1,6 @@
+object
+MainTest
+{
+  foo(a, // comment
+    b)
+}
diff --git a/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/p3/src/main/scala/Test.scala b/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/p3/src/main/scala/Test.scala
new file mode 100644
index 0000000000..a96ec3f1fa
--- /dev/null
+++ b/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/p3/src/main/scala/Test.scala
@@ -0,0 +1,6 @@
+object
+Test
+{
+  foo(a, // comment
+    b)
+}
diff --git a/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/p3/src/test/scala/MainTest.scala b/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/p3/src/test/scala/MainTest.scala
new file mode 100644
index 0000000000..7d4e15448b
--- /dev/null
+++ b/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/p3/src/test/scala/MainTest.scala
@@ -0,0 +1,6 @@
+object
+MainTest
+{
+  foo(a, // comment
+    b)
+}
diff --git a/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/project/build.properties b/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/project/build.properties
new file mode 100644
index 0000000000..27e88aa115
--- /dev/null
+++ b/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/project/build.properties
@@ -0,0 +1 @@
+sbt.version=0.13.13
diff --git a/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/project/plugins.sbt b/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/project/plugins.sbt
new file mode 100644
index 0000000000..87eecfd5e1
--- /dev/null
+++ b/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/project/plugins.sbt
@@ -0,0 +1,3 @@
+addSbtPlugin   (
+  "com.geirsson" % "sbt-scalafmt" % System.getProperty("plugin.version"))
+
diff --git a/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/target/src_managed/Generated.scala b/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/target/src_managed/Generated.scala
new file mode 100644
index 0000000000..e018c2d95e
--- /dev/null
+++ b/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/target/src_managed/Generated.scala
@@ -0,0 +1 @@
+object      DontFormatMe   {    println(1)    }
diff --git a/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/test b/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/test
new file mode 100644
index 0000000000..392519cf36
--- /dev/null
+++ b/scalafmtSbt/src/sbt-test/scalafmt-sbt/helloworld/test
@@ -0,0 +1,12 @@
+> setupGitRepo
+> scalafmt
+> scalafmtTest
+> check
+> scalafmtDiff
+> scalafmtDiffTest
+> check
+> scalafmt --diff-branch master
+> scalafmt --diff
+> scalafmt --diff --test
+> check
+
diff --git a/utils/src/main/scala/org/scalafmt/util/GitOps.scala b/utils/src/main/scala/org/scalafmt/util/GitOps.scala
index a09b6b6a2e..8490a7a87d 100644
--- a/utils/src/main/scala/org/scalafmt/util/GitOps.scala
+++ b/utils/src/main/scala/org/scalafmt/util/GitOps.scala
@@ -2,10 +2,12 @@ package org.scalafmt.util
 
 import scala.sys.process.ProcessLogger
 import scala.util.Try
+import scala.util.control.NonFatal
 
 import java.io.File
 
 trait GitOps {
+  def diff(branch: String): Seq[AbsoluteFile]
   def lsTree: Seq[AbsoluteFile]
   def rootDir: Option[AbsoluteFile]
 }
@@ -15,20 +17,29 @@ object GitOps {
 }
 
 class GitOpsImpl(workingDirectory: AbsoluteFile) extends GitOps {
-  val swallowStderr = ProcessLogger(_ => Unit, _ => Unit)
-  val baseCommand = Seq("git")
 
   def exec(cmd: Seq[String]): String = {
-    sys.process
-      .Process(cmd, workingDirectory.jfile)
-      .!!(swallowStderr)
-      .trim
+    val lastError = new StringBuilder
+    val swallowStderr = ProcessLogger(_ => Unit, err => lastError.append(err))
+    try {
+      sys.process
+        .Process(cmd, workingDirectory.jfile)
+        .!!(swallowStderr)
+        .trim
+    } catch {
+      case NonFatal(e) =>
+        throw new IllegalStateException(
+          s"Failed to run command ${cmd.mkString(" ")}. " +
+            s"Error: ${lastError.toString()}",
+          e)
+    }
   }
 
   override def lsTree: Seq[AbsoluteFile] =
     Try {
       exec(
-        baseCommand ++ Seq(
+        Seq(
+          "git",
           "ls-tree",
           "-r",
           "HEAD",
@@ -41,9 +52,26 @@ class GitOpsImpl(workingDirectory: AbsoluteFile) extends GitOps {
 
   override def rootDir: Option[AbsoluteFile] =
     Try {
-      val cmd = baseCommand ++ Seq("rev-parse", "--show-toplevel")
+      val cmd = Seq(
+        "git",
+        "rev-parse",
+        "--show-toplevel"
+      )
       val result = AbsoluteFile.fromFile(new File(exec(cmd)), workingDirectory)
       require(result.jfile.isDirectory)
       result
     }.toOption
+
+  override def diff(branch: String): Seq[AbsoluteFile] = {
+    exec(
+      Seq(
+        "git",
+        "diff",
+        "--name-only",
+        "HEAD",
+        branch
+      )).lines.map { x =>
+      AbsoluteFile.fromFile(new File(x), workingDirectory)
+    }.toSeq
+  }
 }