diffcore-rename: split out the delta counting code.

This is to rework diffcore break/rename/copy detection code
so that it does not affected when deltifier code gets improved.

Signed-off-by: Junio C Hamano <junkio@cox.net>

diffcore-delta.c

@@ -0,0 +1,43 @@
+#include "cache.h"
+#include "diff.h"
+#include "diffcore.h"
+#include "delta.h"
+#include "count-delta.h"
+
+static int diffcore_count_changes_1(void *src, unsigned long src_size,
+				    void *dst, unsigned long dst_size,
+				    unsigned long delta_limit,
+				    unsigned long *src_copied,
+				    unsigned long *literal_added)
+{
+	void *delta;
+	unsigned long delta_size;
+
+	delta = diff_delta(src, src_size,
+			   dst, dst_size,
+			   &delta_size, delta_limit);
+	if (!delta)
+		/* If delta_limit is exceeded, we have too much differences */
+		return -1;
+
+	/* Estimate the edit size by interpreting delta. */
+	if (count_delta(delta, delta_size, src_copied, literal_added)) {
+		free(delta);
+		return -1;
+	}
+	free(delta);
+	return 0;
+}
+
+int diffcore_count_changes(void *src, unsigned long src_size,
+			   void *dst, unsigned long dst_size,
+			   unsigned long delta_limit,
+			   unsigned long *src_copied,
+			   unsigned long *literal_added)
+{
+	return diffcore_count_changes_1(src, src_size,
+					dst, dst_size,
+					delta_limit,
+					src_copied,
+					literal_added);
+}