About hg-fast-export : Fast Mercurial to Git converter!
More Information: http://repo.or.cz/w/fast-export.git
Steps:

1. Launch Terminal by pressing command+space, type terminal and hit Enter key.
2. Run

   ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)" < /dev/null 2> /dev/null

3. Install

   brew install hg-fast-export

Done!