Create RefValue container

ugit/base.py

@@ -84,7 +84,7 @@ def read_tree(tree_oid):
 def commit(message):
     commit = f"tree {write_tree()}\n"
 
-    HEAD = data.get_ref("HEAD")
+    HEAD = data.get_ref("HEAD").value
     if HEAD:
         commit += f"parent {HEAD}\n"
 
@@ -93,23 +93,23 @@ def commit(message):
 
     oid = data.hash_object(commit.encode(), "commit")
 
-    data.update_ref("HEAD", oid)
+    data.update_ref("HEAD", data.RefValue(symbolic=False, value=oid))
 
     return oid
 
 
 def create_tag(name, oid):
-    data.update_ref(f"refs/tags/{name}", oid)
+    data.update_ref(f"refs/tags/{name}", data.RefValue(symbolic=False, value=oid))
 
 
 def checkout(oid):
     commit = get_commit(oid)
     read_tree(commit.tree)
-    data.update_ref("HEAD", oid)
+    data.update_ref("HEAD", data.RefValue(symbolic=False, value=oid))
 
 
 def create_branch(name, oid):
-    data.update_ref(f"refs/heads/{name}", oid)
+    data.update_ref(f"refs/heads/{name}", data.RefValue(symbolic=False, value=oid))
 
 
 Commit = namedtuple("Commit", ["tree", "parent", "message"])
@@ -161,8 +161,8 @@ def get_oid(name):
         f"refs/heads/{name}",
     ]
     for ref in refs_to_try:
-        if data.get_ref(ref):
-            return data.get_ref(ref)
+        if data.get_ref(ref).value:
+            return data.get_ref(ref).value
 
     # Name is SHA1
     is_hex = all(c in string.hexdigits for c in name)

ugit/cli.py

@@ -123,8 +123,8 @@ def k(args):
     oids = set()
     for refname, ref in data.iter_refs():
         dot += f"'{refname}' [shape=note]\n"
-        dot += f"'{refname}' -> '{ref}'\n"
-        oids.add(ref)
+        dot += f"'{refname}' -> '{ref.value}'\n"
+        oids.add(ref.value)
 
     for oid in base.iter_commits_and_parents(oids):
         commit = base.get_commit(oid)

ugit/data.py

@@ -3,6 +3,8 @@ from pathlib import Path, PurePath
 import hashlib
 import os
 
+from collections import namedtuple
+
 GIT_DIR = ".ugit"
 
 
@@ -11,11 +13,15 @@ def init():
     Path.mkdir(f"{GIT_DIR}/objects")
 
 
-def update_ref(ref, oid):
+RefValue = namedtuple("RefValue", ["symbolic", "value"])
+
+
+def update_ref(ref, value):
+    assert not value.symbolic
     ref_path = f"{GIT_DIR}/{ref}"
     Path.mkdir(ref_path, exist_ok=True)
     with open(ref_path, "w") as f:
-        f.write(oid)
+        f.write(value.value)
 
 
 def get_ref(ref):
@@ -28,7 +34,7 @@ def get_ref(ref):
     if value and value.startswith("ref:"):
         return get_ref(value.split(":", 1)[1].strip())
 
-    return value
+    return RefValue(symbolic=False, value=value)
 
 
 def iter_refs():