ScalafmtSession: add check for git constraint

scalafmt-dynamic/src/main/scala/org/scalafmt/dynamic/ScalafmtDynamicSession.scala

@@ -21,6 +21,8 @@ final case class ScalafmtDynamicSession(
   override def matchesProjectFilters(file: Path): Boolean =
     cfg.isIncludedInProject(file)
 
+  override def isGitOnly: Boolean = cfg.projectIsGit
+
   private def tryFormat(
       file: Path,
       code: String

scalafmt-dynamic/src/main/scala/org/scalafmt/dynamic/ScalafmtReflectConfig.scala

@@ -29,6 +29,9 @@ class ScalafmtReflectConfig private[dynamic] (val fmtReflect: ScalafmtReflect)(
       target.invoke("indent")
   }
 
+  lazy val projectIsGit =
+    Try(projectField.invokeAs[Boolean]("git")).getOrElse(false)
+
   @inline def getVersion = fmtReflect.version
 
   @inline def isIncludedInProject(path: Path): Boolean =

scalafmt-dynamic/src/test/scala/org/scalafmt/dynamic/DynamicSuite.scala

@@ -477,6 +477,14 @@ class DynamicSuite extends FunSuite {
     assertEquals(error, "Missing version")
   }
 
+  private def assertDynamicConfig(
+      fmt: Format
+  )(f: ScalafmtReflectConfig => Unit): Unit =
+    fmt.dynamic.resolveConfig(fmt.config) match {
+      case Left(e) => fail("failed to load config", e)
+      case Right(cfg) => f(cfg)
+    }
+
   private def checkDynamicConfig(
       name: String,
       version: String,
@@ -485,13 +493,22 @@ class DynamicSuite extends FunSuite {
   )(f: ScalafmtReflectConfig => Unit): Unit = {
     check(s"$name [v=$version d=$dialect]") { fmt =>
       fmt.setVersion(version, dialect, rest: _*)
-      fmt.dynamic.resolveConfig(fmt.config) match {
-        case Left(e) => fail("failed to load config", e)
-        case Right(cfg) => f(cfg)
-      }
+      assertDynamicConfig(fmt)(f)
     }
   }
 
+  checkExhaustive("check project.git=true") { _ => "project.git = true" } {
+    (f, _) => assertDynamicConfig(f)(x => assertEquals(x.projectIsGit, true))
+  }
+
+  checkExhaustive("check project.git=false") { _ => "project.git = false" } {
+    (f, _) => assertDynamicConfig(f)(x => assertEquals(x.projectIsGit, false))
+  }
+
+  checkExhaustive("check project.git missing") { _ => "" } { (f, _) =>
+    assertDynamicConfig(f)(x => assertEquals(x.projectIsGit, false))
+  }
+
   checkDynamicConfig(
     s"check indent.main",
     "3.0.0",

scalafmt-interfaces/src/main/java/org/scalafmt/interfaces/ScalafmtSession.java

@@ -26,4 +26,9 @@ public interface ScalafmtSession {
      */
     boolean matchesProjectFilters(Path file);
 
+    /**
+     * Whether this configuration intends to limit files to those managed by git.
+     */
+    boolean isGitOnly();
+
 }