Tagging all messages in certain threads

[Christoph Ludwig <cludwig@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>]

Hi,

Since I have only a limited disk quota I use folder hooks to purge all
messages older than some limit in my mailing list folders. But if I
took part in a discussion I want to keep this particular thread.

Now it is easy to exclude all messages sent by me from the pattern
that determines which messages to purge when I enter a mail
folder:

  folder-hook =Abo/mutt* 
'push<delete-pattern>~r>21d!(~F|~N|~fcludwig@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx|~fMajordomo.mutt.org)<enter><sync-mailbox>'

But how can I tell mutt that it shall not delete any messages that
belong to a thread in which I took part? (Or more general: How can I
tag all threads that contain messages that match a given pattern?)

Thanks in advance

Christoph

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