This would provide support for "muted" threads, as well as allowing for negative
filtering based on messages not matched by the original search, (but present in
threads that do have at least one matched message).
notmuch command-line tool
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+Implement "notmuch search --exclude-threads=<search-terms>" to allow
+for excluding muted threads, (and any other negative, thread-based
+filtering that the user wants to do).
+
Fix "notmuch show" so that the UI doesn't fail to show a thread that
is visible in a search buffer, but happens to no longer match the
current search. (Perhaps add a --matching=<secondary-search-terms>