1 files changed, 77 insertions, 0 deletions
diff --git a/git/db/py/ref.py b/git/db/py/ref.py
new file mode 100644
index 00000000..951f0437
--- /dev/null
+++ b/git/db/py/ref.py
@@ -0,0 +1,77 @@
+# Copyright (C) 2010, 2011 Sebastian Thiel (byronimo@gmail.com) and contributors
+#
+# This module is part of GitDB and is released under
+# the New BSD License: http://www.opensource.org/licenses/bsd-license.php
+from base import PureCompoundDB
+
+import os
+__all__ = ('PureReferenceDB', )
+
+class PureReferenceDB(PureCompoundDB):
+	"""A database consisting of database referred to in a file"""
+	
+	# Configuration
+	# Specifies the object database to use for the paths found in the alternates
+	# file. If None, it defaults to the PureGitODB
+	ObjectDBCls = None
+	
+	def __init__(self, ref_file):
+		super(PureReferenceDB, self).__init__()
+		self._ref_file = ref_file
+		
+	def _set_cache_(self, attr):
+		if attr == '_dbs':
+			self._dbs = list()
+			self._update_dbs_from_ref_file()
+		else:
+			super(PureReferenceDB, self)._set_cache_(attr)
+		# END handle attrs
+		
+	def _update_dbs_from_ref_file(self):
+		dbcls = self.ObjectDBCls
+		if dbcls is None:
+			# late import
+			from git import PureGitODB
+			dbcls = PureGitODB
+		# END get db type
+		
+		# try to get as many as possible, don't fail if some are unavailable
+		ref_paths = list()
+		try:
+			ref_paths = [l.strip() for l in open(self._ref_file, 'r').readlines()]
+		except (OSError, IOError):
+			pass
+		# END handle alternates
+		
+		ref_paths_set = set(ref_paths)
+		cur_ref_paths_set = set(db.root_path() for db in self._dbs)
+		
+		# remove existing
+		for path in (cur_ref_paths_set - ref_paths_set):
+			for i, db in enumerate(self._dbs[:]):
+				if db.root_path() == path:
+					del(self._dbs[i])
+					continue
+				# END del matching db
+		# END for each path to remove
+		
+		# add new
+		# sort them to maintain order
+		added_paths = sorted(ref_paths_set - cur_ref_paths_set, key=lambda p: ref_paths.index(p))
+		for path in added_paths:
+			try:
+				db = dbcls(path)
+				# force an update to verify path
+				if isinstance(db, PureCompoundDB):
+					db.databases()
+				# END verification
+				self._dbs.append(db)
+			except Exception, e:
+				# ignore invalid paths or issues
+				pass
+		# END for each path to add
+		
+	def update_cache(self, force=False):
+		# re-read alternates and update databases
+		self._update_dbs_from_ref_file()
+		return super(PureReferenceDB, self).update_cache(force)