The dev client can bedownloaded from here, these files are all needed to test the client fully. You only need to download the updates files, the file date will indicate when they were changed. DayZ_code will usually be the only file to change, so once you have the others, there is no need to redownload them. This is a manual update and you will need to revert your client to connect to the live servers.

http://gaming.hngamers.com/devclient