docs: clarify why fetch_repository_data excludes purgatory

Add comments explaining that PR event processing (both incoming and
purgatory) should only use database announcements, not purgatory ones.

This is intentional because:
- Incoming PR events should only be accepted for validated announcements
- Purgatory PR events should only be released when announcement is promoted
- This prevents accepting PR events for announcements that fail validation

Differs from state event processing which uses fetch_repository_data_with_purgatory
because state events check authorization without releasing from purgatory.

1 files changed, 3 insertions, 0 deletions

diff --git a/src/git/sync.rs b/src/git/sync.rs
index a0b7c47..4b35023 100644
--- a/src/git/sync.rs
+++ b/src/git/sync.rs
@@ -1171,6 +1171,9 @@ async fn process_purgatory_pr_events(
     );
 
     // Fetch repository data for syncing
+    // NOTE: Only fetch from database, NOT purgatory. PR events should only be
+    // released from purgatory when the announcement has been promoted (validated).
+    // This ensures we don't accept PR events for announcements that fail validation.
     let db_repo_data = match fetch_repository_data(database, identifier).await {
         Ok(data) => data,
         Err(e) => {