Uniform use of user supplied vocabulary

Author: sbidoul

news/7811.feature

@@ -1,2 +1,2 @@
-Generate PEP 376 REQUESTED metadata for top level requirements installed
+Generate PEP 376 REQUESTED metadata for user supplied requirements installed
 by pip.

src/pip/_internal/req/req_set.py

@@ -108,7 +108,7 @@ def add_requirement(
 
         # This next bit is really a sanity check.
         assert not install_req.user_supplied or parent_req_name is None, (
-            "a direct req shouldn't have a parent"
+            "a user supplied req shouldn't have a parent"
         )
 
         # Unnamed requirements are scanned again and the requirement won't be
@@ -164,8 +164,8 @@ def add_requirement(
         # If we're now installing a constraint, mark the existing
         # object for real installation.
         existing_req.constraint = False
-        # If we're now installing a top level requirement, mark the existing
-        # object as top level.
+        # If we're now installing a user supplied requirement,
+        # mark the existing object as such.
         if install_req.user_supplied:
             existing_req.user_supplied = True
         existing_req.extras = tuple(sorted(