cli: add support for notmuch search --duplicate=N with --output=messages

Print the message IDs of all messages matching the search terms that
have at least N files associated with them.

2 files changed, 39 insertions, 8 deletions

diff --git a/doc/man1/notmuch-search.rst b/doc/man1/notmuch-search.rst
index b6607c92..8110086e 100644
--- a/doc/man1/notmuch-search.rst
+++ b/doc/man1/notmuch-search.rst
@@ -142,10 +142,14 @@ Supported options for **search** include
         rather than the number of matching messages.
 
     ``--duplicate=N``
-        Effective with ``--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.
+        For ``--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.
+
+        For ``--output=messages``, only output message IDs of messages
+        matching the search terms that have at least N filenames
+        associated with them.
 
         Note that this option is orthogonal with the **folder:** search
         prefix. The prefix matches messages based on filenames. This
diff --git a/notmuch-search.c b/notmuch-search.c
index 671fe413..6345fb62 100644
--- a/notmuch-search.c
+++ b/notmuch-search.c
@@ -311,6 +311,24 @@ process_address_header (const search_options_t *opt, const char *value)
 }
 
 static int
+_count_filenames (notmuch_message_t *message)
+{
+    notmuch_filenames_t *filenames;
+    int i = 0;
+
+    filenames = notmuch_message_get_filenames (message);
+
+    while (notmuch_filenames_valid (filenames)) {
+        notmuch_filenames_move_to_next (filenames);
+        i++;
+    }
+
+    notmuch_filenames_destroy (filenames);
+
+    return i;
+}
+
+static int
 do_search_messages (search_options_t *opt)
 {
     notmuch_message_t *message;
@@ -357,10 +375,13 @@ do_search_messages (search_options_t *opt)
 	    notmuch_filenames_destroy( filenames );
 
 	} else if (opt->output == OUTPUT_MESSAGES) {
-	    format->set_prefix (format, "id");
-	    format->string (format,
-			    notmuch_message_get_message_id (message));
-	    format->separator (format);
+            /* special case 1 for speed */
+            if (opt->dupe <= 1 || opt->dupe <= _count_filenames (message)) {
+                format->set_prefix (format, "id");
+                format->string (format,
+                                notmuch_message_get_message_id (message));
+                format->separator (format);
+            }
 	} else {
 	    if (opt->output & OUTPUT_SENDER) {
 		const char *addrs;
@@ -503,6 +524,12 @@ notmuch_search_command (notmuch_config_t *config, int argc, char *argv[])
     if (! opt.output)
 	opt.output = OUTPUT_SUMMARY;
 
+    if (opt.output != OUTPUT_FILES && opt.output != OUTPUT_MESSAGES &&
+	opt.dupe != -1) {
+        fprintf (stderr, "Error: --duplicate=N is only supported with --output=files and --output=messages.\n");
+        return EXIT_FAILURE;
+    }
+
     switch (format_sel) {
     case NOTMUCH_FORMAT_TEXT:
 	opt.format = sprinter_text_create (config, stdout);