Merge pull request #20874 from igfoo/igfoo/overlay

C++: Add the beginnings of overlay support

Author: igfoo

cpp/downgrades/a42ce5fc943254097f85471b94ae2247e819104a/old.dbscheme

@@ -0,0 +1,4 @@
+description: Add databaseMetadata and overlayChangedFiles relations
+compatibility: full
+databaseMetadata.rel: delete
+overlayChangedFiles.rel: delete

cpp/downgrades/a42ce5fc943254097f85471b94ae2247e819104a/semmlecode.dbscheme

@@ -21,3 +21,4 @@ dataExtensions:
   - ext/deallocation/*.model.yml
   - ext/allocation/*.model.yml
 warnOnImplicitThis: true
+compileForOverlayEval: true

cpp/downgrades/a42ce5fc943254097f85471b94ae2247e819104a/upgrade.properties

@@ -1,3 +1,4 @@
+
 /*- Compilations -*/
 
 /**
@@ -2378,6 +2379,24 @@ link_parent(
     int link_target : @link_target ref
 );
 
+/**
+ * The CLI will automatically emit applicable tuples for this table,
+ * such as `databaseMetadata("isOverlay", "true")` when building an
+ * overlay database.
+ */
+databaseMetadata(
+  string metadataKey: string ref,
+  string value: string ref
+);
+
+/**
+ * The CLI will automatically emit tuples for each new/modified/deleted file
+ * when building an overlay database.
+ */
+overlayChangedFiles(
+  string path: string ref
+);
+
 /*- XML Files -*/
 
 xmlEncoding(