Add implementation of merge-certs command

sop-java-picocli/src/main/kotlin/sop/cli/picocli/commands/MergeCertsCmd.kt

@@ -0,0 +1,48 @@
+// SPDX-FileCopyrightText: 2024 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package sop.cli.picocli.commands
+
+import picocli.CommandLine
+import picocli.CommandLine.Command
+import sop.cli.picocli.SopCLI
+import sop.exception.SOPGPException
+import java.io.IOException
+
+@Command(
+    name = "merge-certs",
+    resourceBundle = "msg_merge-certs",
+    exitCodeOnInvalidInput = SOPGPException.UnsupportedOption.EXIT_CODE)
+class MergeCertsCmd : AbstractSopCmd() {
+
+    @CommandLine.Option(names = ["--no-armor"], negatable = true)
+    var armor = false
+
+    @CommandLine.Parameters(paramLabel = "CERTS")
+    var updates: List<String> = listOf()
+
+    override fun run() {
+        val mergeCerts = throwIfUnsupportedSubcommand(SopCLI.getSop().mergeCerts(), "merge-certs")
+
+        if (!armor) {
+            mergeCerts.noArmor()
+        }
+
+        for (certFileName in updates) {
+            try {
+                getInput(certFileName).use { mergeCerts.updates(it) }
+            } catch (e: IOException) {
+                throw RuntimeException(e)
+            }
+        }
+
+        try {
+
+            val ready = mergeCerts.baseCertificates(System.`in`)
+            ready.writeTo(System.out)
+        } catch (e: IOException) {
+            throw RuntimeException(e)
+        }
+    }
+}