In 0.10.2 a new feature was added for backing up files that are replaced by the file.managed and file.recurse states. The new feature is called the backup mode. Setting the backup mode is easy, but is can be set in a number of places.
The backup_mode can be set in the minion config file:
backup_mode: minion
Or it can be set for each file:
/etc/ssh/sshd_config:
file.managed:
- source: salt://ssh/sshd_config
- backup: minion
The files will be saved in the minion cachedir under the directory named file_backup. The files will be in the location relative to where they were under the root filesystem and be appended with a timestamp. This should make them easy to browse.