Check git is available or warn user. Fixes #112. (#114)

piku-bootstrap

@@ -21,6 +21,9 @@ main() {
     echo
   fi
 
+  # check git dependencies
+  command -v git > /dev/null || bail "This script depends on git. Please install it to continue.";
+
   # ensure we have a dir
   mkdir -p "${PBD}"
 
@@ -147,4 +150,9 @@ install_virtualenv() {
           || bail_install;
 }
 
+bail() {
+  echo "$@"
+  exit 1;
+}
+
 main "$@"