Bash: https://github.com/donnemartin/gitsome#enabling-bash-complet...
Zsh: https://github.com/donnemartin/gitsome/issues/2#issuecomment...
Adding this line to the ~/.xonshrc file fixed the reported behaviour: $BASH_COMPLETIONS.append('/usr/share/doc/git-1.8.3.1/contrib/completion/git-completion.bash')
Adding this line to the ~/.xonshrc file fixed the reported behaviour: $BASH_COMPLETIONS.append('/usr/share/doc/git-1.8.3.1/contrib/completion/git-completion.bash')