private static void UpdateRef(string refToUpdate, string refToUpdateTo)
{
Files.AssertInRepo();
// Get the hash that `refToUpdateTo` points at.
var hash = Refs.Hash(refToUpdateTo);
// Abort if `refToUpdateTo` does not point at a hash.
if (!Objects.Exists(hash))
{
throw new Exception(refToUpdateTo + " not a valid SHA1");
}
// Abort if `refToUpdate` does not match the syntax of a ref.
if (!Refs.IsRef(refToUpdate))
{
throw new Exception("cannot lock the ref " + refToUpdate);
}
// Abort if `hash` points to an object in the `objects` directory
// that is not a commit.
if (Objects.Type(Objects.Read(hash)) != "commit")
{
var branch = Refs.TerminalRef(refToUpdate);
throw new Exception(branch + " cannot refer to non-commit object " + hash + "\n");
}
// Otherwise, set the contents of the file that the ref represents
// to `hash`.
Refs.Write(Refs.TerminalRef(refToUpdate), hash);
}