stg refresh crashes when a file has "copied" status

[matyasselmeci]

When detects a file is a copy, it can end up having the "copied" status in the repo - this causes stg refresh to crash with the message not expecting 'C' copied status with porcelain v2. Backtrace:

thread 'main' panicked at src/stupid/status.rs:138:21:
not expecting 'C' copied status with porcelain v2
stack backtrace:
   0: __rustc::rust_begin_unwind
             at /rustc/29483883eed69d5fb4db01964cdf2af4d86e9cb2/library/std/src/panicking.rs:697:5
   1: core::panicking::panic_fmt
             at /rustc/29483883eed69d5fb4db01964cdf2af4d86e9cb2/library/core/src/panicking.rs:75:14
   2: stg::stupid::status::Status::from_char
   3: stg::cmd::refresh::assemble_refresh_tree
   4: stg::cmd::refresh::run
   5: stg::execute_command
   6: stg::main

This is how I can reproduce it:

mkdir testrepo && cd testrepo
echo hi > hi
git init; git add hi; git commit -m initial
stg init; stg new mypatch -m mypatch
cp hi hi2
git add -N hi2
echo bye >> hi

git status --short now shows

 M hi
 C hi -> hi2

and running stg refresh results in the above crash.

Versions:

Stacked Git 2.5.4
git version 2.46.0