Add references when deleting attachments

app/src/main/java/eu/faircode/email/Core.java

@@ -2111,7 +2111,11 @@ class Core {
             throw new MessageRemovedException();
 
         String msgid = EntityMessage.generateMessageId();
+        String ref = (TextUtils.isEmpty(message.references)
+                ? message.msgid
+                : message.references + " " + message.msgid);
         MimeMessage icopy = new MimeMessageEx((MimeMessage) imessage, msgid);
+        icopy.addHeader("References", MessageHelper.limitReferences(ref));
         MessageHelper helper = new MessageHelper(icopy, context);
         MessageHelper.MessageParts parts = helper.getMessageParts();
         List<MessageHelper.AttachmentPart> aparts = parts.getAttachmentParts();

app/src/main/java/eu/faircode/email/MessageHelper.java

@@ -372,19 +372,8 @@ public class MessageHelper {
             imessage.addHeader("Sensitivity", "Company-Confidential");
 
         // References
-        if (message.references != null) {
+        if (message.references != null)
-            // https://tools.ietf.org/html/rfc5322#section-2.1.1
+            imessage.addHeader("References", limitReferences(message.references));
-            // Each line of characters MUST be no more than 998 characters ... , excluding the CRLF.
-            String references = message.references;
-            int maxlen = MAX_HEADER_LENGTH - "References: ".length();
-            int sp = references.indexOf(' ');
-            while (references.length() > maxlen && sp > 0) {
-                Log.i("Dropping reference=" + references.substring(0, sp));
-                references = references.substring(sp);
-                sp = references.indexOf(' ');
-            }
-            imessage.addHeader("References", references);
-        }
 
         if (message.inreplyto != null)
             imessage.addHeader("In-Reply-To", message.inreplyto);
@@ -820,6 +809,17 @@ public class MessageHelper {
         return new InternetAddress(email, name, StandardCharsets.UTF_8.name());
     }
 
+    static String limitReferences(String references) {
+        int maxlen = MAX_HEADER_LENGTH - "References: ".length();
+        int sp = references.indexOf(' ');
+        while (references.length() > maxlen && sp > 0) {
+            Log.i("Dropping reference=" + references.substring(0, sp));
+            references = references.substring(sp);
+            sp = references.indexOf(' ');
+        }
+        return references;
+    }
+
     static Pair<String, String> getExtra(String email, String extra) {
         String name = null;
         int comma = extra.indexOf(',');