Only write files when content changes

Previously the CLI would call `File.write` for every file, even if the contents was unchanged. This unnecessary filesystem churn can have a knock-on effect on other tools which may be watching directories for changes (e.g. IDEs). This commit updates the `stree write` command so that it only performs a write when the file contents has changed.

Author: davidtaylorhq

lib/syntax_tree/cli.rb

@@ -303,10 +303,11 @@ def run(item)
             options.print_width,
             options: options.formatter_options
           )
+        changed = source != formatted
 
-        File.write(filepath, formatted) if item.writable?
+        File.write(filepath, formatted) if item.writable? && changed
 
-        color = source == formatted ? Color.gray(filepath) : filepath
+        color = changed ? filepath : Color.gray(filepath)
         delta = ((Time.now - start) * 1000).round
 
         puts "#{color} #{delta}ms"