Allow to return in reply to

plugins/messageviewerplugins/externalscriptplugin/README

@@ -11,4 +11,4 @@ Arguments:
 - %cc returns "cc"
 - %from returns "from"
 - %bcc returns "bcc"
-
+- %inreplyto returns "replyto"

plugins/messageviewerplugins/externalscriptplugin/viewerpluginexternalscriptparseargument.cpp

@@ -53,6 +53,9 @@ QStringList ViewerPluginExternalScriptParseArgument::parse(const QStringList &sc
         } else if (arg == QString::fromLatin1("%body")) {
             const QByteArray body = mMessage ? mMessage->body() : Q_NULLPTR;
             newArguments << QStringLiteral("\"%1\"").arg(QLatin1String(body));
+        } else if (arg == QString::fromLatin1("%inreplyto")) {
+            KMime::Headers::InReplyTo *inReplyTo = mMessage ? mMessage->inReplyTo(false) : Q_NULLPTR;
+            newArguments << QStringLiteral("\"%1\"").arg(inReplyTo ? inReplyTo->asUnicodeString() : QString());
         } else {
             newArguments << arg;
         }