Refactor.
Split 'common/' into commit '0d34ea6a3bcc9c85a0866b7af2cddd3028b5b69e'

git-subtree-dir: common
git-subtree-mainline: b7da1bb75135fc644e1ecf6cc8d06fe7b2cf01bb
git-subtree-split: 0d34ea6a3bcc9c85a0866b7af2cddd3028b5b69e