db/update/InotifyUpdate: handle IN_CREATE without IN_ISDIR

A new symlink causes `IN_CREATE`.  Usually, we catch `IN_CREATE` only with
IN_ISDIR to watch the new directory, but otherwise `IN_CREATE` is not
handled.  Regular files are "created" but they have usable content
only with `IN_CLOSE_WRITE`.  Yet symlinks have only `IN_CREATE` and
they are immediately usable.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/2192

NEWS

@@ -1,6 +1,8 @@
 ver 0.23.17 (not yet released)
 * storage
   - nfs: require libnfs 4.0 or later
+* database
+  - inotify: trigger update after symlink was created
 * support libfmt 11.1
 
 ver 0.23.16 (2024/12/03)

src/db/update/InotifyUpdate.cxx

@@ -293,6 +293,10 @@ InotifyUpdate::InotifyCallback(int wd, unsigned mask,
 	}
 
 	if ((mask & (IN_CLOSE_WRITE|IN_MOVE|IN_DELETE)) != 0 ||
+	    /* regular file or symlink was created; this check is only
+	       interesting for symlinks because regular files have
+	       usable content only after IN_CLOSE_WRITE */
+	    (mask & (IN_CREATE|IN_ISDIR)) == IN_CREATE ||
 	    /* at the maximum depth, we watch out for newly created
 	       directories */
 	    (directory.GetDepth() == max_depth &&