From: Daniel Kahn Gillmor <dkg@fifthhorseman.net>

This new function asks the database to reindex a given message.
The parameter `indexopts` is currently ignored, but is intended to
provide an extensible API to support e.g. changing the encryption or
filtering status (e.g. whether and how certain non-plaintext parts are
indexed).
---
 lib/message.cc | 46 +++++++++++++++++++++++++++++++++++++++++++++-
 lib/notmuch.h  | 14 ++++++++++++++
 2 files changed, 59 insertions(+), 1 deletion(-)

diff --git a/lib/message.cc b/lib/message.cc
index a7bd38ac..193eedb2 100644
--- a/lib/message.cc
+++ b/lib/message.cc
@@ -579,7 +579,9 @@ void
 _notmuch_message_remove_terms (notmuch_message_t *message, const char *prefix)
 {
     Xapian::TermIterator i;
-    size_t prefix_len = strlen (prefix);
+    size_t prefix_len = 0;
+
+    prefix_len = strlen (prefix);
 
     while (1) {
 	i = message->doc.termlist_begin ();
@@ -1916,3 +1918,45 @@ _notmuch_message_frozen (notmuch_message_t *message)
 {
     return message->frozen;
 }
+
+notmuch_status_t
+notmuch_message_reindex (notmuch_message_t *message,
+			 notmuch_param_t unused (*indexopts))
+{
+    notmuch_database_t *notmuch = NULL;
+    notmuch_status_t ret = NOTMUCH_STATUS_SUCCESS, status;
+    notmuch_private_status_t private_status;
+    notmuch_filenames_t *orig_filenames = NULL;
+    const char *filename = NULL;
+
+    if (message == NULL)
+	return NOTMUCH_STATUS_NULL_POINTER;
+
+    notmuch = _notmuch_message_database (message);
+
+    orig_filenames = notmuch_message_get_filenames (message);
+
+    private_status = _notmuch_message_remove_indexed_terms (message);
+    if (private_status)
+	return COERCE_STATUS(private_status, "error removing terms");
+
+    /* re-add the filenames with the associated indexopts */
+    for (; notmuch_filenames_valid (orig_filenames);
+	 notmuch_filenames_move_to_next (orig_filenames)) {
+	filename = notmuch_filenames_get (orig_filenames);
+
+	status = notmuch_database_add_message(notmuch,
+					      filename,
+					      &message);
+	if (status != NOTMUCH_STATUS_SUCCESS &&
+	    status != NOTMUCH_STATUS_DUPLICATE_MESSAGE_ID) {
+	    /* if we failed to add this filename, go ahead and try the
+	     * next one as though it were first, but report the
+	     * error... */
+	    ret = status;
+	}
+    }
+
+    /* XXX TODO destroy orig_filenames? */
+    return ret;
+}
diff --git a/lib/notmuch.h b/lib/notmuch.h
index 33e9fd24..11818018 100644
--- a/lib/notmuch.h
+++ b/lib/notmuch.h
@@ -1389,6 +1389,20 @@ notmuch_filenames_t *
 notmuch_message_get_filenames (notmuch_message_t *message);
 
 /**
+ * Re-index the e-mail corresponding to 'message' using the supplied index options
+ *
+ * Returns the status of the re-index operation.  (see the return
+ * codes documented in notmuch_database_add_message)
+ *
+ * After reindexing, the user should discard the message object passed
+ * in here by calling notmuch_message_destroy, since it refers to the
+ * original message, not to the reindexed message.
+ */
+notmuch_status_t
+notmuch_message_reindex (notmuch_message_t *message,
+			 notmuch_param_t *indexopts);
+
+/**
  * Message flags.
  */
 typedef enum _notmuch_message_flag {
-- 
2.11.0