lib: update documentation for notmuch_database_get_directory

Clarify that using the directory after destroying the corresponding
database is not permitted.

This is implicit in the description of notmuch_database_destroy, but
it doesn't hurt to be explicit, and we do express similar "ownership"
relationships at other places in the docs.

1 files changed, 4 insertions, 0 deletions

diff --git a/lib/notmuch.h b/lib/notmuch.h
index 68896ae7..3df1ade7 100644
--- a/lib/notmuch.h
+++ b/lib/notmuch.h
@@ -415,6 +415,10 @@ notmuch_database_end_atomic (notmuch_database_t *notmuch);
  * If this directory object does not exist in the database, this
  * returns NOTMUCH_STATUS_SUCCESS and sets *directory to NULL.
  *
+ * Otherwise the returned directory object is owned by the database
+ * and as such, will only be valid until notmuch_database_destroy is
+ * called.
+ *
  * Return value:
  *
  * NOTMUCH_STATUS_SUCCESS: Successfully retrieved directory.