initial version, can start a server that serves the diff, gen an html file in tmp and open it or generate it in a specific location

difftool.sh

@@ -0,0 +1,39 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+STATIC=""
+OUTFILE=""
+ARGS=()
+
+while [ $# -gt 0 ]; do
+  case "$1" in
+    --static)
+      STATIC="--static"
+      shift
+      ;;
+    --out)
+      if [ $# -lt 2 ]; then
+        echo "Error: --out requires a file path" >&2
+        exit 1
+      fi
+      OUTFILE="$2"
+      shift 2
+      ;;
+    *)
+      ARGS+=("$1")
+      shift
+      ;;
+  esac
+done
+
+if [ ${#ARGS[@]} -lt 3 ]; then
+  echo "Usage: difftool.sh [--static] [--out <file>] <git-project-dir> <main branch> <feature branch> [port]" >&2
+  exit 1
+fi
+
+script_dir="$(cd "$(dirname "$0")" && pwd)"
+node_args=("$script_dir/server.js")
+[ -n "$STATIC" ] && node_args+=("$STATIC")
+[ -n "$OUTFILE" ] && node_args+=("--out" "$OUTFILE")
+node_args+=("${ARGS[@]}")
+exec node "${node_args[@]}"