updater: keep update_history across the metadata rewrite

The update path calls create_documentation_metadata, which writes metadata.json
from scratch, and only then appends the step summary. So update_history never
held more than the last step and a chain of updates lost its history.

Read the history before the rewrite and restore it in merge_into_metadata.

Author: anhnh2002

codewiki/cli/adapters/doc_generator.py

@@ -442,8 +442,11 @@ async def _run_incremental_update(
             )
         working_dir = str(self.output_dir.absolute())
         if record.outcome in ("incremental", "no_change"):
+            # create_documentation_metadata rewrites metadata.json from scratch;
+            # keep the history of earlier updates so a chain of updates accumulates.
+            prior_history = self._read_update_history(working_dir)
             doc_generator.create_documentation_metadata(working_dir, components, len(leaf_nodes))
-            self._merge_update_summary(working_dir)
+            self._merge_update_summary(working_dir, prior_history)
             for file_path in os.listdir(working_dir):
                 if file_path.endswith((".md", ".json")):
                     self.job.files_generated.append(file_path)
@@ -480,7 +483,17 @@ def _move_docs_aside(self) -> None:
         if self.verbose:
             self.progress_tracker.update_stage(0.1, f"Previous docs preserved at {target}")
 
-    def _merge_update_summary(self, working_dir: str) -> None:
+    @staticmethod
+    def _read_update_history(working_dir: str) -> list:
+        path = os.path.join(working_dir, "metadata.json")
+        try:
+            with open(path, encoding="utf-8") as f:
+                history = (json.load(f) or {}).get("update_history")
+        except (OSError, json.JSONDecodeError):
+            return []
+        return history if isinstance(history, list) else []
+
+    def _merge_update_summary(self, working_dir: str, prior_history: list | None = None) -> None:
         record = getattr(self, "_last_update_record", None)
         if record is None:
             return
@@ -490,7 +503,7 @@ def _merge_update_summary(self, working_dir: str) -> None:
         preserved = getattr(self, "_preserved_docs_dir", None)
         if preserved:
             summary["previous_docs"] = preserved
-        merge_into_metadata(working_dir, summary)
+        merge_into_metadata(working_dir, summary, prior_history=prior_history)
         try:
             record.save(working_dir)
         except OSError:

codewiki/src/be/updater/record.py

@@ -96,8 +96,14 @@ def save(self, docs_dir: str) -> str:
         return path
 
 
-def merge_into_metadata(docs_dir: str, summary: dict[str, Any]) -> None:
-    """Append ``summary`` under ``last_update`` (and an ``update_history`` list)."""
+def merge_into_metadata(
+    docs_dir: str, summary: dict[str, Any], prior_history: list[dict[str, Any]] | None = None
+) -> None:
+    """Append ``summary`` under ``last_update`` (and an ``update_history`` list).
+
+    ``prior_history`` restores the history when the caller rewrote metadata.json
+    in between (the update path regenerates it before merging).
+    """
     path = os.path.join(docs_dir, "metadata.json")
     meta: dict[str, Any] = {}
     if os.path.exists(path):
@@ -110,6 +116,8 @@ def merge_into_metadata(docs_dir: str, summary: dict[str, Any]) -> None:
     history = meta.get("update_history")
     if not isinstance(history, list):
         history = []
+    if not history and prior_history:
+        history = list(prior_history)
     history.append(summary)
     meta["update_history"] = history
     with open(path, "w", encoding="utf-8") as f: