Add types to objects

ugit/cli.py

@@ -43,4 +43,4 @@ def hash_object(args):
 
 def cat_file(args):
     sys.stdout.flush()
-    sys.stdout.buffer.write(data.get_object(args.object))
+    sys.stdout.buffer.write(data.get_object(args.object), expected=None)

ugit/data.py

@@ -10,13 +10,21 @@ def init():
     Path.mkdir(f"{GIT_DIR}/objects")
 
 
-def hash_object(data):
+def hash_object(data, type_="blob"):
-    oid = hashlib.sha1(data).hexdigest()
+    obj = type_.encode() + b"\x00" + data
+    oid = hashlib.sha1(obj).hexdigest()
     with open(f"{GIT_DIR}/objects/{oid}", "wb") as out:
-        out.write(data)
+        out.write(obj)
     return oid
 
 
-def get_object(oid):
+def get_object(oid, expected="blob"):
     with open(f"{GIT_DIR}/objects/{oid}", "rb") as f:
-        return f.read()
+        obj = f.read()
+
+    type_, _, content = obj.partition(b"\x00")
+    type_ = type_.decode()
+
+    if expected is not None:
+        assert type_ == expected, f"Expected {expected}, got {type_}"
+    return content