The 'commit' value should be tested and used first when resolving the ref for a layer, since that is an explicit override in each layer index 'layeritem' record.

If should take precedence over more-global 'branch' and 'release' values, instead of being last.

Proposed patch is:

     def get_vcs_reference(self):
+        if self.commit is not None and len(self.commit) > 0:
+            return self.commit
         if self.branch is not None and len(self.branch) > 0:
             return self.branch
         if self.release is not None:
             return self.release.name
-        if self.commit is not None and len(self.commit) > 0:
-            return self.commit
         return 'N/A'