Fix docker versioning with registry port (#686)

Fix issue when retrieving version via tag in `FROM` section.
We also need to consider that the registry may contain a port.

* Update DockerArtifactVersioning.groovy
* add error message for missing image tag in FROM line

src/com/sap/piper/versioning/DockerArtifactVersioning.groovy

@@ -56,7 +56,11 @@ class DockerArtifactVersioning extends ArtifactVersioning {
         def version = null
         for (def i = 0; i < lines.size(); i++) {
             if (lines[i].startsWith('FROM') && lines[i].indexOf(':') > 0) {
-                version = lines[i].split(':')[1]
+                def imageParts = lines[i].split(':')
+                version = imageParts[imageParts.size()-1]
+                if (version.contains('/')) {
+                    script.error "[${getClass().getSimpleName()}] FROM statement does not contain an explicit image version: ${lines[i]} "
+                }
                 break
             }
         }

test/groovy/com/sap/piper/versioning/DockerArtifactVersioningTest.groovy

@@ -51,6 +51,18 @@ class DockerArtifactVersioningTest extends BasePiperTest{
         assertTrue(loggingRule.log.contains('[DockerArtifactVersioning] Version from Docker base image tag: 1.2.3'))
     }
 
+    @Test
+    void testVersioningFromWithRegistryPort() {
+        DockerArtifactVersioning av = new DockerArtifactVersioning(nullScript, [filePath: 'Dockerfile_registryPort', dockerVersionSource: 'FROM'])
+        assertEquals('1.2.3', av.getVersion())
+    }
+
+    @Test
+    void testVersioningFromWithMissingTag() {
+        thrown.expectMessage('FROM statement does not contain an explicit image version')
+        new DockerArtifactVersioning(nullScript, [filePath: 'Dockerfile_registryPortNoTag', dockerVersionSource: 'FROM']).getVersion()
+    }
+
     @Test
     void testVersioningEnv() {
         av = new DockerArtifactVersioning(nullScript, [filePath: 'Dockerfile', dockerVersionSource: 'TEST'])

test/resources/versioning/DockerArtifactVersioning/Dockerfile_registryPort

@@ -0,0 +1,5 @@
+FROM registry:4444/path/image:1.2.3
+
+USER root
+
+ENV TEST 2.3.4

test/resources/versioning/DockerArtifactVersioning/Dockerfile_registryPortNoTag

@@ -0,0 +1,5 @@
+FROM registry:4444/path/image
+
+USER root
+
+ENV TEST 2.3.4