Implement sop version --sop-spec

external-sop/src/main/java/sop/external/operation/VersionExternal.java

@@ -99,4 +99,23 @@ public class VersionExternal implements Version {
             throw new RuntimeException(e);
         }
     }
+
+    @Override
+    public String getSopSpecVersion() {
+        String[] command = new String[] {binary, "version", "--sop-spec"};
+        String[] env = ExternalSOP.propertiesToEnv(environment).toArray(new String[0]);
+        try {
+            Process process = runtime.exec(command, env);
+            BufferedReader stdInput = new BufferedReader(new InputStreamReader(process.getInputStream()));
+            StringBuilder sb = new StringBuilder();
+            String line;
+            while ((line = stdInput.readLine()) != null) {
+                sb.append(line).append('\n');
+            }
+            ExternalSOP.finish(process);
+            return sb.toString();
+        } catch (IOException e) {
+            throw new RuntimeException(e);
+        }
+    }
 }

sop-java-picocli/src/main/java/sop/cli/picocli/commands/VersionCmd.java

@@ -22,6 +22,9 @@ public class VersionCmd extends AbstractSopCmd {
 
         @CommandLine.Option(names = "--backend")
         boolean backend;
+
+        @CommandLine.Option(names = "--sop-spec")
+        boolean sopSpec;
     }
 
 
@@ -45,5 +48,10 @@ public class VersionCmd extends AbstractSopCmd {
             Print.outln(version.getBackendVersion());
             return;
         }
+
+        if (exclusive.sopSpec) {
+            Print.outln(version.getSopSpecVersion());
+            return;
+        }
     }
 }

sop-java/src/main/java/sop/operation/Version.java

@@ -46,4 +46,14 @@ public interface Version {
      * @return extended version string
      */
     String getExtendedVersion();
+
+    /**
+     * Return the revision of the SOP specification that this implementation is implementing, for example,
+     * <pre>draft-dkg-openpgp-stateless-cli-06</pre>.
+     * If the implementation targets a specific draft but the implementer knows the implementation is incomplete,
+     * it should prefix the draft title with a "~" (TILDE, U+007E), for example: <pre>~draft-dkg-openpgp-stateless-cli-06</pre>.
+     *
+     * @return implemented SOP spec version
+     */
+    String getSopSpecVersion();
 }

sop-java/src/testFixtures/java/sop/testsuite/operation/VersionTest.java

@@ -14,6 +14,7 @@ import java.util.stream.Stream;
 
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
 @EnabledIf("sop.testsuite.operation.AbstractSOPTest#hasBackends")
 public class VersionTest extends AbstractSOPTest {
@@ -51,4 +52,11 @@ public class VersionTest extends AbstractSOPTest {
         assertFalse(extended.isEmpty());
     }
 
+    @ParameterizedTest
+    @MethodSource("provideInstances")
+    public void sopSpecVersionTest(SOP sop) {
+        String sopSpec = sop.version().getSopSpecVersion();
+        assertTrue(sopSpec.startsWith("draft-dkg-openpgp-stateless-cli-") ||
+                sopSpec.startsWith("~draft-dkg-openpgp-stateless-cli-"));
+    }
 }