cache: rewrite to support arbitrary validation method

Specifically, the cache can use any portage supported checksum method,
or use the standard mtime approach.  In addition, support controlling
whether or not paths are stored, and generally try to restore some
of the centralization/encapsulation that was in place originally.
(cherry picked from commit bc1aed614fb588f0ade5bcb5d1265a8db0f8d247)

Change-Id: Ic38057e7dbb15063c64a93c99e66e113a7d4c70e

1 files changed, 11 insertions, 7 deletions

diff --git a/pym/portage/repository/config.py b/pym/portage/repository/config.py
index 9a5473820..a67e7f138 100644
--- a/pym/portage/repository/config.py
+++ b/pym/portage/repository/config.py
@@ -128,14 +128,18 @@ class RepoConfig(object):
 		self.manifest_hashes = None
 		self.cache_format = None
 
-	def get_pregenerated_cache(self, auxdbkeys, readonly=True):
-		if self.cache_format is None:
-			return None
-		elif self.cache_format == 'pms':
+	def get_pregenerated_cache(self, auxdbkeys, readonly=True, force=False):
+		format = self.cache_format
+		if format is None:
+			if not force:
+				return None
+			format = 'pms'
+		if format == 'pms':
 			from portage.cache.metadata import database
-			return database(self.location, 'metadata/cache',
-				auxdbkeys, readonly=readonly)
-		return None
+		else:
+			return None
+		return database(self.location, 'metadata/cache',
+			auxdbkeys, readonly=readonly)
 
 	def load_manifest(self, *args, **kwds):
 		kwds['thin'] = self.thin_manifest