Fix git diff script

Author: samlitowitz

scripts/git-has-changes.sh

@@ -1,5 +1,5 @@
 #!/usr/bin/env sh
 
-if [[ -n $(git status --porcelain --untracked-files=no) ]]; then
+if git status --porcelain --untracked-files=no; then
   exit 1
 fi