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To connect two MacBooks Pro and transfer files by Thunderbolt, you need to put one of them in Target Disk mode. To start up in Target Disk mode, hold the T key while your MacBook Pro is starting up until you see the Thunderbolt icon on the display.
In your case, you need to put your old MacBook Pro in Target Disk mode. This mode will convert the MacBook Pro's hard drive onto an external drive, so you can access to it from Finder on the MacBook Pro with Retina display and restore all the files you need with Migration Assistant > http://support.apple.com/kb/HT4413
unfortunately the option to select thunderbolt/firewire never comes up.
It directly goes to the options from where to transfer and then upcon clicking on it. It keeps on looking with the spinner icon showing and it never finds the other computer.
It does see it through the wiresless but not through thunderbolt.
The more I look to make this happen the more I am convinved that this feature is not fully baked and does not really work as the documentation on "Thunderbolt bridge" setup is next to none existent and only one perons through macrumors has supposedly managed this. It is really a shame as I was looking forward to use this new capability.
All the best,
I would check 2 things. Make sure your old MacBook Pro is Thunderbolt. If it has a thunderbolt next to the port it is, however, it it is just a square (like a display) it is not. Second thing, when using the migration assistant, you will need to select "From another disk or Time Machine Back Up". If you say from another Mac, it looks only on the network for another Mac. Hope this helps.
If you really want to use ThunderBolt Target Disk Mode, you will need to Restart the computer with the files in Target Disk Mode. This cannot be done on a Mac with Mac OS X active -- the restart is required:
About connecting with Thunderbolt Bridge (not Target Disk mode) see the article by Iljitsch van Beijnum on Ars Technica:
Apparently you have to do some setup in the Network pref pane.