Well, Since no one seemed to have the answer to this question I started trying to find a way myself to get this done. Here is what I ended up doing if anyone ever has the same problem I did.
I took the command line from this thread
http://forum.xbmc.org/showthread.php?tid=67078
the command to add the nightly updates to your launcher was:
defaults write com.teamxbmc.xbmclauncher XBMCAdditionalDownloadPlistURLs -array-add
http://mirrors.xbmc.org/nightlies/osx/update_urls.plist
I copied the update_urls.plist to my pc and edited it. The plist looks like this:
<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd"><plist version="1.0"><array> <dict> <key>UpdateScript</key> <string>http://atv-xbmc-launcher.googlecode.com/svn/tags/ul-info/scripts/xbmc-nightly_update.sh</string> <key>URL</key> <string>http://mirrors.xbmc.org/nightlies/osx/xbmc-20110515-8b3a9fc-master-x86.dmg</string> <key>Type</key> <string>Application</string> <key>MD5</key> <string>966771ec19664869ac5cb64b21a218bf</string> <key>Name</key> <string>XBMC Rev: 20110515</string> </dict></array></plist>
I then changed it so it would only download the nightly I wanted along with removing the MD5 key check. When finished it looked like this:
<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd"><plist version="1.0"><array> <dict> <key>UpdateScript</key> <string>http://atv-xbmc-launcher.googlecode.com/svn/tags/ul-info/scripts/xbmc-nightly_update.sh</string> <key>URL</key> <string>http://mirrors.xbmc.org/nightlies/osx/xbmc-20110501-194db82-master-x86.dmg</string> <key>Type</key> <string>Application</string> <key>Name</key> <string>XBMC Rev: 20110501</string> </dict></array></plist>
I then saved it and uploaded it to my dropbox.
Then I used filezilla and went to /mnt/Scratch/Users/frontrow/Library/Preferences and copied the file com.teamxbmc.xbmclauncher.plist to my pc and edited it. I erased every entry inside the file and saved it so it was 0 bytes. then copied it back to the apple tv.
I then ssh'd back into my apple tv and instead of running the command so the launcher will download the latest nightly and install it I put in the link to where the file is on my dropbox Like so:
defaults write com.teamxbmc.xbmclauncher XBMCAdditionalDownloadPlistURLs -array-add
http://dl.dropbox.com/u/19094774/update_urls.plist
Now if I want to revert to any nightly I just go to my dropbox and edited the plist with the version I want and save and then on my apple tv it will fetch that nightly.
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