[geary/mjog/709-conversation-trusted-email-tooltip] Set conversation trusted email addresses as tooltips

[Michael Gratton <mjog src gnome org>]

commit 113bb7e8975010bdb846f1b36a4e84633b4d9cd7
Author: Michael Gratton <mike vee net>
Date:   Mon Feb 17 07:49:40 2020 +1100

    Set conversation trusted email addresses as tooltips
    
    This makes abbreviated contact name display consistent with other
    abbreviated forms, and reduces the effort needed to discover the actual
    email address.
    
    See #709

 src/client/conversation-viewer/conversation-message.vala | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/src/client/conversation-viewer/conversation-message.vala 
b/src/client/conversation-viewer/conversation-message.vala
index e6548a6d..3b9a6328 100644
--- a/src/client/conversation-viewer/conversation-message.vala
+++ b/src/client/conversation-viewer/conversation-message.vala
@@ -158,6 +158,7 @@ public class ConversationMessage : Gtk.Grid, Geary.BaseInterface {
                 this.displayed = new Geary.RFC822.MailboxAddress(
                     this.contact.display_name, this.source.address
                 );
+                this.tooltip_text = this.source.address;
             } else {
                 // Display both the display name and the email address
                 // so that the user has the full information at hand