Revert "Merge branch 'en/header-split-cache-h-part-3' into next"

This reverts commit 76ebce0b7a,
reversing changes made to 62e19d66fb,
in preparation for redoing the topic to make it buildable from the
source.

diff-lib.c

@@ -1,21 +1,18 @@
 /*
  * Copyright (C) 2005 Junio C Hamano
  */
-#include "git-compat-util.h"
+#include "cache.h"
 #include "quote.h"
 #include "commit.h"
 #include "diff.h"
 #include "diffcore.h"
 #include "gettext.h"
-#include "hash.h"
 #include "hex.h"
 #include "object-name.h"
-#include "read-cache.h"
 #include "revision.h"
 #include "cache-tree.h"
 #include "unpack-trees.h"
 #include "refs.h"
-#include "repository.h"
 #include "submodule.h"
 #include "symlinks.h"
 #include "trace.h"