Teach lint,pretty to operate on staged copy

Gets a bit crazy.

scripts/common

@@ -4,10 +4,14 @@ cachedJS() {
     git diff --cached --name-only --diff-filter=ACM "*.js" "*.jsx" "*.ts" "*.tsx" | tr '\n' ' '
 }
 
+staged() {
+    git show :"$1"
+}
+
 ugly() {
     local acc=()
     for jsfile in "$@"; do
-        diff "$jsfile" <($(npm bin)/prettier $jsfile) >/dev/null || acc+=("$jsfile")
+        diff <(staged $jsfile) <(staged $jsfile | $(npm bin)/prettier --stdin-filepath $jsfile) >/dev/null || acc+=("$jsfile")
     done
     echo ${acc[@]}
 }

scripts/pretty

@@ -7,6 +7,21 @@ set -e
 uglyFiles=$(ugly $(cachedJS))
 
 if [ -n "$uglyFiles" ]; then
-  prettier --write $uglyFiles
-  git add $uglyFiles
+  for file in "$uglyFiles"; do
+    if cmp -s <(staged $file) "$file"; then
+      prettier --write "$file"
+      git add "$file"
+    else
+      echo "WARN: Staged and working file differ: '$file'"
+      echo "WARN: Moving working file temporarily..."
+      # Get crazy: backup the working copy of the file, paste the staged version in its place, prettify, add, restore backup
+      backup=$(mktemp -p . $file.XXXXXXXXX)
+      mv "$file" "$backup"
+      staged "$file" > "$file"
+      prettier --write "$file"
+      git add "$file"
+      mv "$backup" "$file"
+      echo "WARN: Working file restored"
+    fi
+  done
 fi