Add ref handling and ref-parse command

libwyag.py

@@ -634,3 +634,152 @@ def tree_checkout(repo, tree, path):
             # TODO: Support symlinks (identified by mode 12*****)
             with open(dest, 'wb') as f:
                 f.write(obj.blobdata)
+
+def ref_resolve(repo, ref):
+    path = GitRepository.repo_file(repo, ref)
+
+    # Sometimes, an indirect reference may be broken. This is normal
+    # in one specific case: we're looking for HEAD on a new repository
+    # with no commits. In that case, .git/HEAD points to "ref:
+    # refs/heads/master", but .git/refs/heads/master doesn't exist yet
+    # (since there's no commit for it to refer to).
+    if not os.path.isfile(path):
+        return None
+
+    with open(path, "r") as fp:
+        data = fp.read()[:-1] # Drop final "\n"
+
+    if data.startswith("ref: "):
+        return ref_resolve(repo, data[len("ref: "):])
+    else:
+        return data
+
+def ref_list(repo, path=None):
+    if not path:
+        path = repo_dir(repo, "refs")
+
+    ret = collections.OrderedDict()
+
+    for f in sorted(os.listdir(path)):
+        can = os.path.join(path, f)
+        if os.path.isdir(can):
+            ret[f] = ref_list(repo, can)
+        else:
+            ret[f] = ref_resolve(repo, can)
+
+    return ret
+
+argsp = argsubparsers.add_parser(
+    "tag",
+    help="List and create tags")
+
+argsp.add_argument("-a",
+                   action="store_true",
+                   dest="create_tag_object",
+                   help="Whether to create a tag object")
+
+argsp.add_argument("name",
+                   nargs="?",
+                   help="The new tag's name")
+
+argsp.add_argument("object",
+                   default="HEAD",
+                   nargs="?",
+                   help="The object the new tag will point to")
+
+def cmd_tag(args):
+    repo = repo_find()
+
+    if args.name:
+        tag_create(repo,
+                   args.name,
+                   args.object,
+                   type="object" if args.create_tag_object else "ref")
+    else:
+        refs = ref_list(repo)
+        show_ref(repo, refs["tags"], with_hash=False)
+
+def tag_create(repo, name, ref, create_tag_object=False):
+    sha = object_find(repo, ref)
+
+    if create_tag_object:
+        tag = GitTag(repo)
+        tag.kvlm = collections.OrderedDict()
+        tag.kvlm[b'object'] = sha.encode()
+        tag.kvlm[b'type'] = b'commit'
+        tag.kvlm[b'tag'] = name.encode()
+        tag.kvlm[b'tagger'] = b'Wyag <wyag@example.com>'
+        tag.kvlm[None] = b'Tag generated by wyag'
+        tag_sha = object_write(tag)
+        ref_create(repo, "tags/" + name, tag_sha)
+    else:
+        ref_create(repo, "tags/" + name, sha)
+
+def ref_create(repo, ref_name, sha):
+    with open(repo_file(repo, "refs/" + ref_name), "w") as fp:
+        fp.write(sha + "\n")
+
+def object_resolve(repo, name):
+    """Resolve a name to an object hash in repo.
+
+This function is aware of:
+
+- the HEAD literal
+- short and long hashes
+- tags
+- branches
+- remote branches"""
+    candidates = list()
+    hashRE = re.compile(r"[0-9A-Fa-f]{4,40}$")
+
+    # Abort on empty string
+    if not name.strip():
+        return None
+
+    if name == "HEAD":
+        return [ref_resolve(repo, "HEAD")]
+
+    if hashRE.match(name):
+        name = name.lower()
+        prefix = name[0:2]
+        path = GitRepository.repo_dir(repo, "objects", prefix, mkdir=False)
+        if path:
+            rem = name[2:]
+            for f in os.listdir(path):
+                if f.startswith(rem):
+                    candidates.append(prefix + f)
+
+    # Try for references
+    as_tag = ref_resolve(repo, "refs/tags/" + name)
+    if as_tag:
+        candidates.append(as_tag)
+
+    as_branch = ref_resolve(repo, "refs/heads/" + name)
+    if as_branch:
+        candidates.append(as_branch)
+
+    return candidates
+
+argsp = argsubparsers.add_parser(
+    "rev-parse",
+    help="Parse revision (or other objects) identifiers")
+
+argsp.add_argument("--wyag-type",
+                  metavar="type",
+                  dest="type",
+                  choices=["blob", "commit", "tag", "tree"],
+                  default=None,
+                  help="Specify the expected type")
+
+argsp.add_argument("name",
+                   help="The name to parse")
+
+def cmd_rev_parse(args):
+    if args.type:
+        fmt = args.type.encode()
+    else:
+        fmt = None
+
+    repo = repo_find()
+
+    print(object_find(repo, args.name, fmt, follow=True))