tree-diff.c: move S_DIFFTREE_IFXMIN_NEQ define from cache.h

S_DIFFTREE_IFXMIN_NEQ is *only* used in tree-diff.c, so there is no
point exposing it in cache.h.  Move it to tree-diff.c.

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

cache.h

@@ -10,21 +10,6 @@
 #include "object.h"
 #include "statinfo.h"
 
-/*
- * Some mode bits are also used internally for computations.
- *
- * They *must* not overlap with any valid modes, and they *must* not be emitted
- * to outside world - i.e. appear on disk or network. In other words, it's just
- * temporary fields, which we internally use, but they have to stay in-house.
- *
- * ( such approach is valid, as standard S_IF* fits into 16 bits, and in Git
- *   codebase mode is `unsigned int` which is assumed to be at least 32 bits )
- */
-
-/* used internally in tree-diff */
-#define S_DIFFTREE_IFXMIN_NEQ	0x80000000
-
-
 /*
  * Basic data structures for the directory cache
  */

tree-diff.c

@@ -6,6 +6,19 @@
 #include "diffcore.h"
 #include "tree.h"
 
+/*
+ * Some mode bits are also used internally for computations.
+ *
+ * They *must* not overlap with any valid modes, and they *must* not be emitted
+ * to outside world - i.e. appear on disk or network. In other words, it's just
+ * temporary fields, which we internally use, but they have to stay in-house.
+ *
+ * ( such approach is valid, as standard S_IF* fits into 16 bits, and in Git
+ *   codebase mode is `unsigned int` which is assumed to be at least 32 bits )
+ */
+
+#define S_DIFFTREE_IFXMIN_NEQ	0x80000000
+
 /*
  * internal mode marker, saying a tree entry != entry of tp[imin]
  * (see ll_diff_tree_paths for what it means there)