[PATCH] Detect renames in diff family.

This rips out the rename detection engine from diff-helper and moves it
to the diff core, and updates the internal calling convention used by
diff-tree family into the diff core.  In order to give the same option
name to diff-tree family as well as to diff-helper, I've changed the
earlier diff-helper '-r' option to '-M' (stands for Move; sorry but the
natural abbreviation 'r' for 'rename' is already taken for 'recursive').

Although I did a fair amount of test with the git-diff-tree with
existing rename commits in the core GIT repository, this should still be
considered beta (preview) release.  This patch depends on the diff-delta
infrastructure just committed.

This implements almost everything I wanted to see in this series of
patch, except a few minor cleanups in the calling convention into diff
core, but that will be a separate cleanup patch.

Signed-off-by: Junio C Hamano <junkio@cox.net>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff.h

@@ -17,21 +17,10 @@ extern void diff_change(unsigned mode1, unsigned mode2,
 
 extern void diff_unmerge(const char *path);
 
-/* These are for diff-helper */
+extern void diff_setup(int detect_rename, int minimum_score,
+		       int reverse,
+		       const char **spec, int cnt);
 
-struct diff_spec {
-	unsigned char blob_sha1[20];
-	unsigned short mode;	 /* file mode */
-	unsigned sha1_valid : 1; /* if true, use blob_sha1 and trust mode;
-				  * however with a NULL SHA1, read them
-				  * from the file system.
-				  * if false, use the name and read mode from
-				  * the filesystem.
-				  */
-	unsigned file_valid : 1; /* if false the file does not even exist */
-};
-
-extern void run_external_diff(const char *name, const char *other,
-			      struct diff_spec *, struct diff_spec *);
+extern void diff_flush(void);
 
 #endif /* DIFF_H */