If a subdir exists and is empty, go ahead and clone into it.
If a subdir exists and is empty, go ahead and clone into it.

This will make it easier to support git-submodule and gclient at
the same time.

Review URL: http://codereview.chromium.org/9692022

git-svn-id: bd64dd6fa6f3f0ed0c0666d1018379882b742947@126428 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

svn2github/chromium-depot-tools,svn2github/chromium-depot-tools,svn2github/chromium-depot-tools