keep timestamp only in security dir

removed some code borg had for backwards compatibility with
old borg versions (that had timestamp only in the cache).

now the manifest timestamp is only checked against the manifest-timestamp
file in the security dir, simplifying the code.

src/borg/cache.py

@@ -133,7 +133,7 @@ class SecurityManager:
             with SaveFile(self.location_file) as fd:
                 fd.write(repository_location)
 
-    def assert_no_manifest_replay(self, manifest, key, cache_config=None):
+    def assert_no_manifest_replay(self, manifest, key):
         try:
             with open(self.manifest_ts_file) as fd:
                 timestamp = fd.read()
@@ -144,8 +144,6 @@ class SecurityManager:
         except OSError as exc:
             logger.warning("Could not read previous location file: %s", exc)
             timestamp = ""
-        if cache_config:
-            timestamp = max(timestamp, cache_config.timestamp or "")
         logger.debug("security: determined newest manifest timestamp as %s", timestamp)
         # If repository is older than the cache or security dir something fishy is going on
         if timestamp and timestamp > manifest.timestamp:
@@ -159,25 +157,17 @@ class SecurityManager:
         if self.known() and not self.key_matches(key):
             raise Cache.EncryptionMethodMismatch()
 
-    def assert_secure(self, manifest, key, *, cache_config=None, warn_if_unencrypted=True, lock_wait=None):
+    def assert_secure(self, manifest, key, *, warn_if_unencrypted=True, lock_wait=None):
         # warn_if_unencrypted=False is only used for initializing a new repository.
         # Thus, avoiding asking about a repository that's currently initializing.
         self.assert_access_unknown(warn_if_unencrypted, manifest, key)
-        if cache_config:
-            self._assert_secure(manifest, key, cache_config)
-        else:
-            cache_config = CacheConfig(self.repository, lock_wait=lock_wait)
-            if cache_config.exists():
-                with cache_config:
-                    self._assert_secure(manifest, key, cache_config)
-            else:
-                self._assert_secure(manifest, key)
+        self._assert_secure(manifest, key)
         logger.debug("security: repository checks ok, allowing access")
 
-    def _assert_secure(self, manifest, key, cache_config=None):
+    def _assert_secure(self, manifest, key):
         self.assert_location_matches()
         self.assert_key_type(key)
-        self.assert_no_manifest_replay(manifest, key, cache_config)
+        self.assert_no_manifest_replay(manifest, key)
         if not self.known():
             logger.debug("security: remembering previously unknown repository")
             self.save(manifest, key)
@@ -258,7 +248,6 @@ class CacheConfig:
         self._check_upgrade(self.config_path)
         self.id = self._config.get("cache", "repository")
         self.manifest_id = hex_to_bin(self._config.get("cache", "manifest"))
-        self.timestamp = self._config.get("cache", "timestamp", fallback=None)
         self.ignored_features = set(parse_stringified_list(self._config.get("cache", "ignored_features", fallback="")))
         self.mandatory_features = set(
             parse_stringified_list(self._config.get("cache", "mandatory_features", fallback=""))
@@ -281,7 +270,6 @@ class CacheConfig:
     def save(self, manifest=None):
         if manifest:
             self._config.set("cache", "manifest", manifest.id_str)
-            self._config.set("cache", "timestamp", manifest.timestamp)
             self._config.set("cache", "ignored_features", ",".join(self.ignored_features))
             self._config.set("cache", "mandatory_features", ",".join(self.mandatory_features))
             if not self._config.has_section("integrity"):
@@ -780,7 +768,6 @@ class LocalCache(CacheStatsMixin, FilesCacheMixin, ChunksMixin):
         self.key = manifest.key
         self.repo_objs = manifest.repo_objs
         self.progress = progress
-        self.timestamp = None
         self._txn_active = False
         self.do_cache = os.environ.get("BORG_USE_CHUNKS_ARCHIVE", "yes").lower() in ["yes", "1", "true"]
 
@@ -800,7 +787,7 @@ class LocalCache(CacheStatsMixin, FilesCacheMixin, ChunksMixin):
             self.open()
 
         try:
-            self.security_manager.assert_secure(manifest, self.key, cache_config=self.cache_config)
+            self.security_manager.assert_secure(manifest, self.key)
 
             if not self.check_cache_compatibility():
                 self.wipe_cache()
@@ -1186,7 +1173,6 @@ class NewCache(CacheStatsMixin, FilesCacheMixin, ChunksMixin):
         self.key = manifest.key
         self.repo_objs = manifest.repo_objs
         self.progress = progress
-        self.timestamp = None
         self._txn_active = False
 
         self.path = cache_dir(self.repository, path)
@@ -1200,7 +1186,7 @@ class NewCache(CacheStatsMixin, FilesCacheMixin, ChunksMixin):
 
         self.open()
         try:
-            self.security_manager.assert_secure(manifest, self.key, cache_config=self.cache_config)
+            self.security_manager.assert_secure(manifest, self.key)
 
             if not self.check_cache_compatibility():
                 self.wipe_cache()