Fix various whitespace issues reported by pyflakes

- E201 whitespace after '['
- E202 whitespace before '}'
- E221 multiple spaces before operator
- E222 multiple spaces after operator
- E225 missing whitespace around operator
- E226 missing whitespace around arithmetic operator
- E231 missing whitespace after ','
- E261 at least two spaces before inline comment
- E271 multiple spaces after keyword

Fixed automatically with autopep8:

  git ls-files | grep py$ | xargs autopep8 --in-place \
    --select E201,E202,E221,E222,E225,E226,E231,E261,E271

Change-Id: I367113eb8c847eb460532c7c2f8643f33040308c
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/254601
Reviewed-by: Mike Frysinger <vapier@google.com>
Tested-by: David Pursehouse <dpursehouse@collab.net>

git_command.py

@@ -101,7 +101,7 @@ class _GitCall(object):
     return _git_version
 
   def __getattr__(self, name):
-    name = name.replace('_','-')
+    name = name.replace('_', '-')
     def fun(*cmdv):
       command = [name]
       command.extend(cmdv)