Split git rev-parse --show-toplevel --git-dir on newline

git rev-parse --show-toplevel --git-dir returns the top
level directory and the .git directory on two seperate lines.

Splitting needs to happen explicitly on a newline, or else
paths with spaces will be parsed incorrectly.

Change-Id: Ie851d31ef55be63213fe8dc445f92af1b7a33f7d
Merge "Split git rev-parse --show-toplevel --git-dir on newline"