patman: Make command methods return a CommandResult

Rather than returning a list of things, return an object. That makes it
easier to access the returned items, and easier to extend the return
value later.

Signed-off-by: Simon Glass <sjg@chromium.org>

tools/patman/gitutil.py

@@ -40,7 +40,7 @@ def CountCommitsToBranch():
     """
     pipe = [['git', 'log', '--no-color', '--oneline', '@{upstream}..'],
             ['wc', '-l']]
-    stdout = command.RunPipe(pipe, capture=True, oneline=True)
+    stdout = command.RunPipe(pipe, capture=True, oneline=True).stdout
     patch_count = int(stdout)
     return patch_count