models: Change Track.last_modified from seconds to ms

docs/changelog.rst

@@ -13,6 +13,12 @@ v0.20.0 (UNRELEASED)
 - Add :class:`mopidy.models.Image` model to be returned by
   :meth:`mopidy.core.LibraryController.get_images`. (Part of :issue:`973`)
 
+- Change the semantics of :attr:`mopidy.models.Track.last_modified` to be
+  milliseconds instead of seconds since Unix epoch, or a simple counter,
+  depending on the source of the track. This makes it match the semantics of
+  :attr:`mopidy.models.Playlist.last_modified`. (Fixes: :issue:`678`, PR:
+  :issue:`1036`)
+
 **Core API**
 
 - Deprecate all properties in the core API. The previously undocumented getter

mopidy/models.py

@@ -378,9 +378,10 @@ class Track(ImmutableObject):
     #: The MusicBrainz ID of the track. Read-only.
     musicbrainz_id = None
 
-    #: Integer representing when the track was last modified, exact meaning
-    #: depends on source of track. For local files this is the mtime, for other
-    #: backends it could be a timestamp or simply a version counter.
+    #: Integer representing when the track was last modified. Exact meaning
+    #: depends on source of track. For local files this is the modification
+    #: time in milliseconds since Unix epoch. For other backends it could be an
+    #: equivalent timestamp or simply a version counter.
     last_modified = None
 
     def __init__(self, *args, **kwargs):

mopidy/utils/path.py

@@ -200,7 +200,7 @@ def _find(root, thread_count=10, relative=False, follow=False):
 
 def find_mtimes(root, follow=False):
     results, errors = _find(root, relative=False, follow=follow)
-    mtimes = dict((f, int(st.st_mtime)) for f, st in results.items())
+    mtimes = dict((f, int(st.st_mtime * 1000)) for f, st in results.items())
     return mtimes, errors