Redmine

Can this get merged if it works? #10888 didn't do much to help Gmail's threading. You still get entirely new threads when the status of a ticket changes.

This patch does the following:

• Removes Tracker Name and Issue Status from the Subject.
  • This does not belong in the subject. It's repeated in the email already.
• Adds an X-Redmine-Issue-Tracker header to the email
  • I'm sure someone wants to filter their Redmine bugs by Tracker/classification. That's quite reasonable, but a header is a better place for this data.
• Adds an In-Reply-To header in addition to the References header
  • GMail respects this as do many other MUAs.

Here's the rest of my message that was curiously getting marked as spam:

GMail threads messages by Subject and In-Reply-To. Other MUAs like Mutt have a more sophisticated algorithm for threading emails, but I do not believe this should be considered a bug or deficiency on GMail's part. Simply put, data does not belong in email Subjects. The only thing that should change is a prefix of Re:, Fwd:, etc. Anything else is a gross violation of email and internet etiquette.

Sorry for the ticket noise, but hilariously I've had to break up my message to find the part that Redmine is marking as spam.

In conclusion:

There are people out there that get overwhelmed by a giant sprawl on emails in their Inbox. You're making Redmine a better experience for them, too.

I've attached a patch to #13111 that fixes the threading issues on Gmail and Office 365.