man: document notmuch search --duplicate=N

Document the notmuch search --duplicate=N option.

1 files changed, 20 insertions, 0 deletions

diff --git a/man/man1/notmuch-search.1 b/man/man1/notmuch-search.1
index 2d6ecafc..f69a4cd7 100644
--- a/man/man1/notmuch-search.1
+++ b/man/man1/notmuch-search.1
@@ -80,6 +80,10 @@ Output the filenames of all messages matching the search terms, either
 one per line (\-\-format=text), separated by null characters
 (\-\-format=text0), as a JSON array (\-\-format=json), or as an
 S-Expression list (\-\-format=sexp).
+
+Note that each message may have multiple filenames associated with it.
+All of them are included in the output, unless limited with the
+\-\-duplicate=N option.
 .RE
 .RS 4
 .TP 4
@@ -158,6 +162,22 @@ but the "match count" is the number of matching non-excluded messages in the
 thread, rather than the number of matching messages.
 .RE
 
+.RS 4
+.TP 4
+.BR \-\-duplicate=N
+
+Effective with
+.BR --output=files ,
+output the Nth filename associated with each message matching the
+query (N is 1-based). If N is greater than the number of files
+associated with the message, don't print anything.
+
+Note that this option is orthogonal with the
+.BR folder:
+search prefix. The prefix matches messages based on filenames. This
+option filters filenames of the matching messages.
+.RE
+
 .SH EXIT STATUS
 
 This command supports the following special exit status codes