It's right there in the error message: run two "git config" commands. You have to run those commands as the user that executes the build, so you presumably need to do something like a "sudo su bamboo" before you begin.
The two values will end up in the .gitconfig
file in the home directory of your Bamboo user:
[user]
name = Bamboo Server
email = bamboo@yourcompany.com
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