Add relative path git alternates support

Original patch provided by walken@google.com

Signed-off-by: Jelmer Vernooij <jelmer@samba.org>

dulwich/object_store.py

@@ -421,9 +421,10 @@ class DiskObjectStore(PackBasedObjectStore):
                 l = l.rstrip("\n")
                 if l[0] == "#":
                     continue
-                if not os.path.isabs(l):
-                    continue
-                ret.append(l)
+                if os.path.isabs(l):
+                    ret.append(l)
+                else:
+                    ret.append(os.path.join(self.path, l))
             return ret
         finally:
             f.close()
@@ -452,6 +453,9 @@ class DiskObjectStore(PackBasedObjectStore):
             f.write("%s\n" % path)
         finally:
             f.close()
+
+        if not os.path.isabs(path):
+            path = os.path.join(self.path, path)
         self.alternates.append(DiskObjectStore(path))
 
     def _load_packs(self):

dulwich/tests/test_object_store.py

@@ -250,6 +250,19 @@ class DiskObjectStoreTests(PackBasedObjectStoreTests, TestCase):
             ["/foo/path", "/bar/path"],
             store._read_alternate_paths())
 
+    def test_rel_alternative_path(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(os.path.relpath(alternate_dir, self.store_dir))
+        self.assertEqual(list(alternate_store), list(store.alternates[0]))
+        self.assertIn(b2.id, store)
+        self.assertEqual(b2, store[b2.id])
+
     def test_pack_dir(self):
         o = DiskObjectStore(self.store_dir)
         self.assertEqual(os.path.join(self.store_dir, "pack"), o.pack_dir)