Merge basic support for alternates.

NEWS

@@ -14,6 +14,8 @@
   * ``HttpGitClient`` which supports the smart server protocol over
     HTTP. "dumb" access is not yet supported. (Jelmer Vernooij, #373688)
 
+  * Add basic support for alternates. (Jelmer Vernooij, #810429)
+
  CHANGES
 
   * unittest2 or python >= 2.7 is now required for the testsuite.

dulwich/object_store.py

@@ -226,6 +226,10 @@ class PackBasedObjectStore(BaseObjectStore):
     def __init__(self):
         self._pack_cache = None
 
+    @property
+    def alternates(self):
+        return []
+
     def contains_packed(self, sha):
         """Check if a particular object is present by SHA1 and is packed."""
         for pack in self.packs:
@@ -310,6 +314,11 @@ class PackBasedObjectStore(BaseObjectStore):
         ret = self._get_loose_object(hexsha)
         if ret is not None:
             return ret.type_num, ret.as_raw_string()
+        for alternate in self.alternates:
+            try:
+                return alternate.get_raw(hexsha)
+            except KeyError:
+                pass
         raise KeyError(hexsha)
 
     def add_objects(self, objects):
@@ -338,6 +347,63 @@ class DiskObjectStore(PackBasedObjectStore):
         self.path = path
         self.pack_dir = os.path.join(self.path, PACKDIR)
         self._pack_cache_time = 0
+        self._alternates = None
+
+    @property
+    def alternates(self):
+        if self._alternates is not None:
+            return self._alternates
+        self._alternates = []
+        for path in self._read_alternate_paths():
+            self._alternates.append(DiskObjectStore(path))
+        return self._alternates
+
+    def _read_alternate_paths(self):
+        try:
+            f = GitFile(os.path.join(self.path, "info", "alternates"),
+                    'rb')
+        except (OSError, IOError), e:
+            if e.errno == errno.ENOENT:
+                return []
+            raise
+        ret = []
+        try:
+            for l in f.readlines():
+                l = l.rstrip("\n")
+                if l[0] == "#":
+                    continue
+                if not os.path.isabs(l):
+                    continue
+                ret.append(l)
+            return ret
+        finally:
+            f.close()
+
+    def add_alternate_path(self, path):
+        """Add an alternate path to this object store.
+        """
+        try:
+            os.mkdir(os.path.join(self.path, "info"))
+        except OSError, e:
+            if e.errno != errno.EEXIST:
+                raise
+        alternates_path = os.path.join(self.path, "info/alternates")
+        f = GitFile(alternates_path, 'wb')
+        try:
+            try:
+                orig_f = open(alternates_path, 'rb')
+            except (OSError, IOError), e:
+                if e.errno != errno.ENOENT:
+                    raise
+            else:
+                try:
+                    f.write(orig_f.read())
+                finally:
+                    orig_f.close()
+            f.write("%s\n" % path)
+        finally:
+            f.close()
+        self.alternates.append(DiskObjectStore(path))
 
     def _load_packs(self):
         pack_files = []

dulwich/tests/test_object_store.py

@@ -221,12 +221,33 @@ class DiskObjectStoreTests(PackBasedObjectStoreTests, TestCase):
     def setUp(self):
         TestCase.setUp(self)
         self.store_dir = tempfile.mkdtemp()
+        self.addCleanup(shutil.rmtree, self.store_dir)
         self.store = DiskObjectStore.init(self.store_dir)
 
     def tearDown(self):
         TestCase.tearDown(self)
         PackBasedObjectStoreTests.tearDown(self)
-        shutil.rmtree(self.store_dir)
+
+    def test_alternates(self):
+        alternate_dir = tempfile.mkdtemp()
+        self.addCleanup(shutil.rmtree, alternate_dir)
+        alternate_store = DiskObjectStore(alternate_dir)
+        b2 = make_object(Blob, data="yummy data")
+        alternate_store.add_object(b2)
+        store = DiskObjectStore(self.store_dir)
+        self.assertRaises(KeyError, store.__getitem__, b2.id)
+        store.add_alternate_path(alternate_dir)
+        self.assertEquals(b2, store[b2.id])
+
+    def test_add_alternate_path(self):
+        store = DiskObjectStore(self.store_dir)
+        self.assertEquals([], store._read_alternate_paths())
+        store.add_alternate_path("/foo/path")
+        self.assertEquals(["/foo/path"], store._read_alternate_paths())
+        store.add_alternate_path("/bar/path")
+        self.assertEquals(
+            ["/foo/path", "/bar/path"],
+            store._read_alternate_paths())
 
     def test_pack_dir(self):
         o = DiskObjectStore(self.store_dir)