do not consider stage cached if checksum/cmd has changed (#3993)

dvc/stage/__init__.py

@@ -493,7 +493,11 @@ class Stage(params.StageParams):
             ret.append("changed checksum")
 
     def already_cached(self):
-        return self.deps_cached() and self.outs_cached()
+        return (
+            not self.changed_stage()
+            and self.deps_cached()
+            and self.outs_cached()
+        )
 
     def deps_cached(self):
         return all(not dep.changed() for dep in self.deps)

dvc/stage/imports.py

@@ -23,7 +23,7 @@ def sync_import(stage, dry=False, force=False):
     if dry:
         return
 
-    if not force and not stage.changed_stage() and stage.already_cached():
+    if not force and stage.already_cached():
         stage.outs[0].checkout()
     else:
         stage.deps[0].download(stage.outs[0])

dvc/stage/run.py

@@ -82,7 +82,6 @@ def _is_cached(stage):
     cached = (
         not stage.is_callback
         and not stage.always_changed
-        and not stage.changed_stage()
         and stage.already_cached()
     )
     if cached: