Only add shgit to PS1 if git is installed

dotfiles/shrc

@@ -31,7 +31,7 @@ if [ -d ~/local/man ]; then
 fi
 
 PS1=
-if [ -f ~/code/lucas/env/utils/shgit ]; then
+if command -v git >/dev/null 2>&1 && [ -f ~/code/lucas/env/utils/shgit ]; then
 	. ~/code/lucas/env/utils/shgit
 	export PS1='$(shgit)'
 fi