watchman: when project-metadata isn't provided, don't add it to the…

… XDB query

Summary:
When `project-metadata` isn't provided in the watchman query, instead of adding `AND project_metadata = ""` to the XDB query, just don't add anything.

We then need to bubble up the project_metadata from the found saved state to where we construct the manifold path for the saved state.

Context: we need this for hack to be able to still get a saved state even when our config has changed.

Reviewed By: kmancini

Differential Revision: D61018325

fbshipit-source-id: b01b162adeed5a73fd10c2737c9da1115f0b333e

watchman/telemetry/LogEvent.h

@@ -156,7 +156,7 @@ struct SavedState {
   std::string project;
   std::string path;
   int64_t commit_date = 0;
-  std::string metadata;
+  std::optional<std::string> projectMetadata;
   std::string properties;
   bool success = false;
 
@@ -169,8 +169,8 @@ struct SavedState {
       event.addString("path", path);
     }
     event.addInt("commit_date", commit_date);
-    if (!metadata.empty()) {
-      event.addString("metadata", metadata);
+    if (projectMetadata.has_value()) {
+      event.addString("metadata", projectMetadata.value());
     }
     if (!properties.empty()) {
       event.addString("properties", properties);