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>