title: Makefile, header dependencies
body: <p>Let's say I have a makefile with the rule</p>
  
  <pre><code>%.o: %.c
   gcc -Wall -Iinclude ...
  </code></pre>
  
  <p>I want *.o to be rebuilt whenever a header file changes. Rather than work out a list of dependencies, whenever any header file in <code>/include</code> changes, then all objects in the dir must be rebuilt. </p>
  
  <p>I can't think of a nice way to change the rule to accomodate this, I'm open to suggestions. Bonus points if the list of headers doesn't have to be hard-coded </p>