cleanup: leverage yield from in more places

Change-Id: I4f9cb27d89241d3738486764817b51981444a903
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/390274
Reviewed-by: Aravind Vasudevan <aravindvasudev@google.com>
Commit-Queue: Mike Frysinger <vapier@google.com>
Tested-by: Mike Frysinger <vapier@google.com>

command.py

@@ -476,8 +476,7 @@ class Command:
             top = self.manifest
         yield top
         if not opt.this_manifest_only:
-            for child in top.all_children:
-                yield child
+            yield from top.all_children
 
 
 class InteractiveCommand(Command):

manifest_xml.py

@@ -857,8 +857,7 @@ https://gerrit.googlesource.com/git-repo/+/HEAD/docs/manifest-format.md
         self._Load()
         outer = self._outer_client
         yield outer
-        for tree in outer.all_children:
-            yield tree
+        yield from outer.all_children
 
     @property
     def all_children(self):
@@ -867,8 +866,7 @@ https://gerrit.googlesource.com/git-repo/+/HEAD/docs/manifest-format.md
         for child in self._submanifests.values():
             if child.repo_client:
                 yield child.repo_client
-                for tree in child.repo_client.all_children:
-                    yield tree
+                yield from child.repo_client.all_children
 
     @property
     def path_prefix(self):

platform_utils.py

@@ -193,10 +193,9 @@ def _walk_windows_impl(top, topdown, onerror, followlinks):
     for name in dirs:
         new_path = os.path.join(top, name)
         if followlinks or not islink(new_path):
-            for x in _walk_windows_impl(
+            yield from _walk_windows_impl(
                 new_path, topdown, onerror, followlinks
-            ):
-                yield x
+            )
     if not topdown:
         yield top, dirs, nondirs