[commands/cache] Be explicit about `pip cache` only working on the wheel cache.

news/6391.feature

@@ -1 +1 @@
-Add ``pip cache`` command for inspecting/managing pip's cache.
+Add ``pip cache`` command for inspecting/managing pip's wheel cache.

src/pip/_internal/commands/__init__.py

@@ -66,7 +66,7 @@ commands_dict = OrderedDict([
     )),
     ('cache', CommandInfo(
         'pip._internal.commands.cache', 'CacheCommand',
-        "Inspect and manage pip's cache.",
+        "Inspect and manage pip's wheel cache.",
     )),
     ('wheel', CommandInfo(
         'pip._internal.commands.wheel', 'WheelCommand',

src/pip/_internal/commands/cache.py

@@ -20,7 +20,7 @@ logger = logging.getLogger(__name__)
 
 class CacheCommand(Command):
     """
-        Inspect and manage pip's cache.
+        Inspect and manage pip's wheel cache.
 
         Subcommands: