checkout: always confirm link type

Currently whether or not link confirmation will run depends on
particular filesystem and existing workspace link type, which introduces
inconsistency in behaviour, where we sometimes catch unsupported links
before touching user data and sometimes we don't.

dvc/objects/checkout.py

@@ -97,13 +97,13 @@ def _link(cache, from_info, to_info):
         raise CheckoutError([str(to_info)]) from exc
 
 
-def _cache_is_copy(cache, path_info):
+def _confirm_cache_type(cache, path_info):
     """Checks whether cache uses copies."""
     if cache.cache_type_confirmed:
-        return cache.cache_types[0] == "copy"
+        return
 
     if set(cache.cache_types) <= {"copy"}:
-        return True
+        return
 
     workspace_file = path_info.with_name("." + uuid())
     test_cache_file = cache.path_info / ".cache_type_test_file"
@@ -118,7 +118,6 @@ def _cache_is_copy(cache, path_info):
         cache.fs.remove(test_cache_file)
 
     cache.cache_type_confirmed = True
-    return cache.cache_types[0] == "copy"
 
 
 def _relink(cache, cache_info, fs, path_info, in_cache, force):
@@ -143,10 +142,13 @@ def _checkout_file(
 ):
     """The file is changed we need to checkout a new copy"""
     modified = False
+
+    _confirm_cache_type(cache, path_info)
+
     cache_info = cache.hash_to_path_info(change.new.oid.value)
     if change.old.oid:
         if relink:
-            if fs.iscopy(path_info) and _cache_is_copy(cache, path_info):
+            if fs.iscopy(path_info) and cache.cache_types[0] == "copy":
                 cache.unprotect(path_info)
             else:
                 _relink(