Add Dockerfile.customInstruction method to be able to use Dockerfile …

…instructions not implemented in the DSL

README.md

@@ -115,6 +115,23 @@ docker / dockerfile := NativeDockerfile(file("subdirectory") / "Dockerfile")
 
 Have a look at [DockerfileExamples](examples/DockerfileExamples.scala) for different ways of defining a Dockerfile.
 
+#### Missing Dockerfile instructions
+
+Dockerfile instructions that are missing from the sbt-docker DSL can still be used by calling the `.customInstruction(instructionName, arguments)` method.
+Example:
+```scala
+new Dockerfile {
+  customInstruction("FROM", "openjdk AS stage1")
+  run("build")
+
+  customInstruction("FROM", "openjdk AS stage2")
+  customInstruction("COPY", "--from=stage1 /path/to/file /path/to/file")
+  customInstruction("STOPSIGNAL", "SIGQUIT")
+
+  entryPoint("application")
+}
+```
+
 ### Building an image
 
 To build an image use the `docker` task.

src/main/scala/sbtdocker/DockerfileCommands.scala

@@ -311,4 +311,20 @@ trait DockerfileCommands {
   def healthCheckShell(commands: String*): T = healthCheckShell(commands)
 
   def healthCheckNone(): T = addInstruction(HealthCheckNone)
+
+  /**
+    * Adds a custom Dockerfile instruction that is not currently supported by this DSL.
+    *
+    * @example
+    * {{{
+    *   // Copy in a multi-stage Dockerfile
+    *   // Equivalent to: "COPY --from=stage1 /path/to/file /path/to/file"
+    *   customInstruction("COPY", "--from=stage1 /path/to/file /path/to/file")
+    *
+    *   // Onbuild instruction can be represented as:
+    *   // ONBUILD RUN /usr/local/bin/python-build --dir /app/src
+    *   customInstruction("ONBUILD", "RUN /usr/local/bin/python-build --dir /app/src")
+    * }}}
+    */
+  def customInstruction(instructionName: String, arguments: String): T = addInstruction(Raw(instructionName, arguments))
 }

src/test/scala/sbtdocker/DockerfileLikeSuite.scala

@@ -34,7 +34,8 @@ class DockerfileLikeSuite extends AnyFunSuite with Matchers {
       .exec(Seq("cmd", "arg"), interval = Some(20.seconds), timeout = Some(10.seconds), startPeriod = Some(1.second), retries = Some(3)),
     HealthCheck
       .shell(Seq("cmd", "arg"), interval = Some(20.seconds), timeout = Some(10.seconds), startPeriod = Some(1.second), retries = Some(3)),
-    HealthCheck.none
+    HealthCheck.none,
+    Raw("COPY", "--from=stage1 /path/to/file /path/to/file")
   )
 
   test("Instructions string is in correct order and matches instructions") {
@@ -62,7 +63,8 @@ class DockerfileLikeSuite extends AnyFunSuite with Matchers {
         |ONBUILD RUN ["echo", "123"]
         |HEALTHCHECK --interval=20s --timeout=10s --start-period=1s --retries=3 CMD ["cmd", "arg"]
         |HEALTHCHECK --interval=20s --timeout=10s --start-period=1s --retries=3 CMD cmd arg
-        |HEALTHCHECK NONE""".stripMargin
+        |HEALTHCHECK NONE
+        |COPY --from=stage1 /path/to/file /path/to/file""".stripMargin
   }
 
   def staged(dockerfile: immutable.Dockerfile): StagedDockerfile = {
@@ -118,6 +120,7 @@ class DockerfileLikeSuite extends AnyFunSuite with Matchers {
         retries = Some(3)
       )
       .healthCheckNone()
+      .customInstruction("COPY", "--from=stage1 /path/to/file /path/to/file")
 
     withMethods shouldEqual predefined
   }

src/test/scala/sbtdocker/InstructionsSpec.scala

@@ -113,4 +113,12 @@ class InstructionsSpec extends AnyFlatSpec with Matchers {
       """LABEL com.example.bar="foo" com.example.bor="boz""""
     Label("foo=bar").toString shouldEqual "LABEL foo=bar"
   }
+
+  "Raw" should "create a correct string" in {
+    Raw(
+      "ONBUILD",
+      "RUN /usr/local/bin/python-build --dir /app/src"
+    ).toString shouldEqual "ONBUILD RUN /usr/local/bin/python-build --dir /app/src"
+    Raw("COPY", "--from=stage1 /path/to/file /path/to/file").toString shouldEqual "COPY --from=stage1 /path/to/file /path/to/file"
+  }
 }

src/test/scala/sbtdocker/immutable/ImmutableDockerfileSpec.scala

@@ -67,6 +67,7 @@ class ImmutableDockerfileSpec extends AnyFlatSpec with Matchers {
         retries = Some(3)
       )
       .healthCheckNone()
+      .customInstruction("COPY", "--from=stage1 /path/to/file /path/to/file")
 
     val instructions = Seq(
       From("image"),
@@ -108,7 +109,8 @@ class ImmutableDockerfileSpec extends AnyFlatSpec with Matchers {
         startPeriod = Some(1.second),
         retries = Some(3)
       ),
-      HealthCheckNone
+      HealthCheckNone,
+      Raw("COPY", "--from=stage1 /path/to/file /path/to/file")
     )
 
     dockerfile.instructions should contain theSameElementsInOrderAs instructions

src/test/scala/sbtdocker/mutable/MutableDockerfileSpec.scala

@@ -66,6 +66,7 @@ class MutableDockerfileSpec extends AnyFlatSpec with Matchers {
         retries = Some(3)
       )
       healthCheckNone()
+      customInstruction("COPY", "--from=stage1 /path/to/file /path/to/file")
     }
 
     val instructions = Seq(
@@ -107,7 +108,8 @@ class MutableDockerfileSpec extends AnyFlatSpec with Matchers {
         startPeriod = Some(1.second),
         retries = Some(3)
       ),
-      HealthCheckNone
+      HealthCheckNone,
+      Raw("COPY", "--from=stage1 /path/to/file /path/to/file")
     )
 
     dockerfile.instructions should contain theSameElementsInOrderAs instructions