'repo' is a tool initially developed for Android development, but it is not specific to Android. At Linaro we use repo to manage the OE source trees too. 

To install repo, you need to follow the instructions here http://source.android.com/source/downloading.html. 

I agree that this is missing from the Linaro ARMv8 release notes https://wiki.linaro.org/HowTo/ARMv8/OpenEmbedded, and it should be added.

I would recommend your remove everything, and restart with a fresh install of repo. i don't really understand your initial log error, tbh... 

nico