[PATCH] diff overhaul

This cleans up the way calls are made into the diff core from diff-tree
family and diff-helper.  Earlier, these programs had "if
(generating_patch)" sprinkled all over the place, but those ugliness are
gone and handled uniformly from the diff core, even when not generating
patch format.

This also allowed diff-cache and diff-files to acquire -R
(reverse) option to generate diff in reverse.  Users of
diff-tree can swap two trees easily so I did not add -R there.

[ Linus' note: I'll add -R to "diff-tree" too, since a "commit
  diff" doesn't have another tree to switch around: the other
  tree is always the parent(s) of the commit ]

Also -M<digits-as-mantissa> suggestion made by Linus has been
implemented.

Documentation updates are also included.

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

Documentation/git-diff-cache.txt

@@ -9,7 +9,7 @@ git-diff-cache - Compares content and mode of blobs between the cache and reposi
 
 SYNOPSIS
 --------
-'git-diff-cache' [-p] [-r] [-z] [-m] [-M] [--cached] <tree-ish>
+'git-diff-cache' [-p] [-r] [-z] [-m] [-M] [-R] [--cached] <tree-ish>
 
 DESCRIPTION
 -----------
@@ -36,6 +36,9 @@ OPTIONS
 -M::
 	Detect renames; implies -p.
 
+-R::
+	Output diff in reverse.
+
 --cached::
 	do not consider the on-disk file at all
 

Documentation/git-diff-files.txt

@@ -9,7 +9,7 @@ git-diff-files - Compares files in the working tree and the cache
 
 SYNOPSIS
 --------
-'git-diff-files' [-p] [-q] [-r] [-z] [-M] [<pattern>...]
+'git-diff-files' [-p] [-q] [-r] [-z] [-M] [-R] [<pattern>...]
 
 DESCRIPTION
 -----------
@@ -26,6 +26,9 @@ OPTIONS
 -q::
 	Remain silent even on nonexisting files
 
+-R::
+	Output diff in reverse.
+
 -M::
 	Detect renames; implies -p.
 

diff-cache.c

@@ -6,15 +6,13 @@ static int generate_patch = 0;
 static int match_nonexisting = 0;
 static int line_termination = '\n';
 static int detect_rename = 0;
+static int reverse_diff = 0;
+static int diff_score_opt = 0;
 
 /* A file entry went away or appeared */
 static void show_file(const char *prefix, struct cache_entry *ce, unsigned char *sha1, unsigned int mode)
 {
-	if (generate_patch)
-		diff_addremove(prefix[0], ntohl(mode), sha1, ce->name, NULL);
-	else
-		printf("%s%06o\tblob\t%s\t%s%c", prefix, ntohl(mode),
-		       sha1_to_hex(sha1), ce->name, line_termination);
+	diff_addremove(prefix[0], ntohl(mode), sha1, ce->name, NULL);
 }
 
 static int get_stat_data(struct cache_entry *ce, unsigned char **sha1p, unsigned int *modep)
@@ -64,7 +62,6 @@ static int show_modified(struct cache_entry *old,
 {
 	unsigned int mode, oldmode;
 	unsigned char *sha1;
-	char old_sha1_hex[60];
 
 	if (get_stat_data(new, &sha1, &mode) < 0) {
 		if (report_missing)
@@ -79,15 +76,8 @@ static int show_modified(struct cache_entry *old,
 	mode = ntohl(mode);
 	oldmode = ntohl(oldmode);
 
-	if (generate_patch)
-		diff_change(oldmode, mode,
-			    old->sha1, sha1, old->name, NULL);
-	else {
-		strcpy(old_sha1_hex, sha1_to_hex(old->sha1));
-		printf("*%06o->%06o\tblob\t%s->%s\t%s%c", oldmode, mode,
-		       old_sha1_hex, sha1_to_hex(sha1),
-		       old->name, line_termination);
-	}
+	diff_change(oldmode, mode,
+		    old->sha1, sha1, old->name, NULL);
 	return 0;
 }
 
@@ -127,10 +117,7 @@ static int diff_cache(struct cache_entry **ac, int entries)
 				break;
 			/* fallthru */
 		case 3:
-			if (generate_patch)
-				diff_unmerge(ce->name);
-			else
-				printf("U %s%c", ce->name, line_termination);
+			diff_unmerge(ce->name);
 			break;
 
 		default:
@@ -166,7 +153,7 @@ static void mark_merge_entries(void)
 }
 
 static char *diff_cache_usage =
-"git-diff-cache [-p] [-r] [-z] [-m] [-M] [--cached] <tree-ish>";
+"git-diff-cache [-p] [-r] [-z] [-m] [-M] [-R] [--cached] <tree-ish>";
 
 int main(int argc, char **argv)
 {
@@ -188,14 +175,19 @@ int main(int argc, char **argv)
 			generate_patch = 1;
 			continue;
 		}
-		if (!strcmp(arg, "-M")) {
+		if (!strncmp(arg, "-M", 2)) {
 			generate_patch = detect_rename = 1;
+			diff_score_opt = diff_scoreopt_parse(arg);
 			continue;
 		}
 		if (!strcmp(arg, "-z")) {
 			line_termination = '\0';
 			continue;
 		}
+		if (!strcmp(arg, "-R")) {
+			reverse_diff = 1;
+			continue;
+		}
 		if (!strcmp(arg, "-m")) {
 			match_nonexisting = 1;
 			continue;
@@ -210,8 +202,9 @@ int main(int argc, char **argv)
 	if (argc != 2 || get_sha1(argv[1], tree_sha1))
 		usage(diff_cache_usage);
 
-	if (generate_patch)
-		diff_setup(detect_rename, 0, 0, 0, 0);
+	diff_setup(detect_rename, diff_score_opt, reverse_diff,
+		   (generate_patch ? -1 : line_termination),
+		   0, 0);
 
 	mark_merge_entries();
 
@@ -222,7 +215,6 @@ int main(int argc, char **argv)
 		die("unable to read tree object %s", argv[1]);
 
 	ret = diff_cache(active_cache, active_nr);
-	if (generate_patch)
-		diff_flush();
+	diff_flush();
 	return ret;
 }

diff-files.c

@@ -7,11 +7,13 @@
 #include "diff.h"
 
 static const char *diff_files_usage =
-"git-diff-files [-p] [-q] [-r] [-z] [-M] [paths...]";
+"git-diff-files [-p] [-q] [-r] [-z] [-M] [-R] [paths...]";
 
 static int generate_patch = 0;
 static int line_termination = '\n';
 static int detect_rename = 0;
+static int reverse_diff = 0;
+static int diff_score_opt = 0;
 static int silent = 0;
 
 static int matches_pathspec(struct cache_entry *ce, char **spec, int cnt)
@@ -31,36 +33,19 @@ static int matches_pathspec(struct cache_entry *ce, char **spec, int cnt)
 
 static void show_unmerge(const char *path)
 {
-	if (generate_patch)
-		diff_unmerge(path);
-	else
-		printf("U %s%c", path, line_termination);
+	diff_unmerge(path);
 }
 
 static void show_file(int pfx, struct cache_entry *ce)
 {
-	if (generate_patch)
-		diff_addremove(pfx, ntohl(ce->ce_mode), ce->sha1,
-			       ce->name, NULL);
-	else
-		printf("%c%06o\t%s\t%s\t%s%c",
-		       pfx, ntohl(ce->ce_mode), "blob",
-		       sha1_to_hex(ce->sha1), ce->name, line_termination);
+	diff_addremove(pfx, ntohl(ce->ce_mode), ce->sha1, ce->name, NULL);
 }
 
 static void show_modified(int oldmode, int mode,
 			  const unsigned char *old_sha1, const unsigned char *sha1,
 			  char *path)
 {
-	char old_sha1_hex[41];
-	strcpy(old_sha1_hex, sha1_to_hex(old_sha1));
-
-	if (generate_patch)
-		diff_change(oldmode, mode, old_sha1, sha1, path, NULL);
-	else
-		printf("*%06o->%06o\tblob\t%s->%s\t%s%c",
-		       oldmode, mode, old_sha1_hex, sha1_to_hex(sha1), path,
-		       line_termination);
+	diff_change(oldmode, mode, old_sha1, sha1, path, NULL);
 }
 
 int main(int argc, char **argv)
@@ -80,7 +65,10 @@ int main(int argc, char **argv)
 			; /* no-op */
 		else if (!strcmp(argv[1], "-z"))
 			line_termination = 0;
-		else if (!strcmp(argv[1], "-M")) {
+		else if (!strcmp(argv[1], "-R"))
+			reverse_diff = 1;
+		else if (!strncmp(argv[1], "-M", 2)) {
+			diff_score_opt = diff_scoreopt_parse(argv[1]);
 			detect_rename = generate_patch = 1;
 		}
 		else
@@ -96,8 +84,9 @@ int main(int argc, char **argv)
 		exit(1);
 	}
 
-	if (generate_patch)
-		diff_setup(detect_rename, 0, 0, 0, 0);		
+	diff_setup(detect_rename, diff_score_opt, reverse_diff,
+		   (generate_patch ? -1 : line_termination),
+		   0, 0);
 
 	for (i = 0; i < entries; i++) {
 		struct stat st;
@@ -117,12 +106,12 @@ int main(int argc, char **argv)
 			i--; /* compensate for loop control increments */
 			continue;
 		}
- 
+
 		if (lstat(ce->name, &st) < 0) {
 			if (errno != ENOENT) {
 				perror(ce->name);
 				continue;
-			}	
+			}
 			if (silent)
 				continue;
 			show_file('-', ce);
@@ -139,7 +128,6 @@ int main(int argc, char **argv)
 		show_modified(oldmode, mode, ce->sha1, null_sha1,
 			      ce->name);
 	}
-	if (generate_patch)
-		diff_flush();
+	diff_flush();
 	return 0;
 }

diff-helper.c

@@ -7,6 +7,7 @@
 #include "diff.h"
 
 static int detect_rename = 0;
+static int diff_score_opt = 0;
 
 static int parse_oneside_change(const char *cp, int *mode,
 				unsigned char *sha1, char *path)
@@ -19,15 +20,15 @@ static int parse_oneside_change(const char *cp, int *mode,
 		cp++;
 	}
 	*mode = m;
-	if (strncmp(cp, "\tblob\t", 6))
+	if (strncmp(cp, "\tblob\t", 6) && strncmp(cp, " blob ", 6))
 		return -1;
 	cp += 6;
 	if (get_sha1_hex(cp, sha1))
 		return -1;
 	cp += 40;
-	if (*cp++ != '\t')
+	if ((*cp != '\t') && *cp != ' ')
 		return -1;
-	strcpy(path, cp);
+	strcpy(path, ++cp);
 	return 0;
 }
 
@@ -63,7 +64,7 @@ static int parse_diff_raw_output(const char *buf)
 			new_mode = (new_mode << 3) | (ch - '0');
 			cp++;
 		}
-		if (strncmp(cp, "\tblob\t", 6))
+		if (strncmp(cp, "\tblob\t", 6) && strncmp(cp, " blob ", 6))
 			return -1;
 		cp += 6;
 		if (get_sha1_hex(cp, old_sha1))
@@ -75,9 +76,9 @@ static int parse_diff_raw_output(const char *buf)
 		if (get_sha1_hex(cp, new_sha1))
 			return -1;
 		cp += 40;
-		if (*cp++ != '\t')
+		if ((*cp != '\t') && *cp != ' ')
 			return -1;
-		strcpy(path, cp);
+		strcpy(path, ++cp);
 		diff_change(old_mode, new_mode, old_sha1, new_sha1, path, 0);
 		break;
 	default:
@@ -101,15 +102,17 @@ int main(int ac, const char **av) {
 			reverse = 1;
 		else if (av[1][1] == 'z')
 			line_termination = 0;
-		else if (av[1][1] == 'M')
+		else if (av[1][1] == 'M') {
 			detect_rename = 1;
+			diff_score_opt = diff_scoreopt_parse(av[1]);
+		}
 		else
 			usage(diff_helper_usage);
 		ac--; av++;
 	}
 	/* the remaining parameters are paths patterns */
 
-	diff_setup(detect_rename, 0, reverse, av+1, ac-1);
+	diff_setup(detect_rename, diff_score_opt, reverse, -1, av+1, ac-1);
 
 	while (1) {
 		int status;

diff-tree.c

@@ -11,6 +11,7 @@ static int read_stdin = 0;
 static int line_termination = '\n';
 static int generate_patch = 0;
 static int detect_rename = 0;
+static int diff_score_opt = 0;
 static const char *header = NULL;
 static const char *header_prefix = "";
 
@@ -84,21 +85,13 @@ static void show_file(const char *prefix, void *tree, unsigned long size, const
 			die("corrupt tree sha %s", sha1_to_hex(sha1));
 
 		show_tree(prefix, tree, size, newbase);
-		
+
 		free(tree);
 		free(newbase);
 		return;
 	}
 
-	if (generate_patch) {
-		if (!S_ISDIR(mode))
-			diff_addremove(prefix[0], mode, sha1, base, path);
-	}
-	else
-		printf("%s%06o\t%s\t%s\t%s%s%c", prefix, mode,
-		       S_ISDIR(mode) ? "tree" : "blob",
-		       sha1_to_hex(sha1), base, path,
-		       line_termination);
+	diff_addremove(prefix[0], mode, sha1, base, path);
 }
 
 static int compare_tree_entry(void *tree1, unsigned long size1, void *tree2, unsigned long size2, const char *base)
@@ -107,7 +100,6 @@ static int compare_tree_entry(void *tree1, unsigned long size1, void *tree2, uns
 	const char *path1, *path2;
 	const unsigned char *sha1, *sha2;
 	int cmp, pathlen1, pathlen2;
-	char old_sha1_hex[50];
 
 	sha1 = extract(tree1, size1, &path1, &mode1);
 	sha2 = extract(tree2, size2, &path2, &mode2);
@@ -151,17 +143,7 @@ static int compare_tree_entry(void *tree1, unsigned long size1, void *tree2, uns
 	if (silent)
 		return 0;
 
-	if (generate_patch) {
-		if (!S_ISDIR(mode1))
-			diff_change(mode1, mode2, sha1, sha2, base, path1);
-	}
-	else {
-		strcpy(old_sha1_hex, sha1_to_hex(sha1));
-		printf("*%06o->%06o\t%s\t%s->%s\t%s%s%c", mode1, mode2,
-		       S_ISDIR(mode1) ? "tree" : "blob",
-		       old_sha1_hex, sha1_to_hex(sha2), base, path1,
-		       line_termination);
-	}
+	diff_change(mode1, mode2, sha1, sha2, base, path1);
 	return 0;
 }
 
@@ -287,11 +269,12 @@ static int diff_tree_sha1_top(const unsigned char *old,
 			      const unsigned char *new, const char *base)
 {
 	int ret;
-	if (generate_patch)
-		diff_setup(detect_rename, 0, 0, 0, 0);
+
+	diff_setup(detect_rename, diff_score_opt, 0,
+		   (generate_patch ? -1 : line_termination),
+		   0, 0);
 	ret = diff_tree_sha1(old, new, base);
-	if (generate_patch)
-		diff_flush();
+	diff_flush();
 	return ret;
 }
 
@@ -301,15 +284,15 @@ static int diff_root_tree(const unsigned char *new, const char *base)
 	void *tree;
 	unsigned long size;
 
-	if (generate_patch)
-		diff_setup(detect_rename, 0, 0, 0, 0);
+	diff_setup(detect_rename, diff_score_opt, 0,
+		   (generate_patch ? -1 : line_termination),
+		   0, 0);
 	tree = read_object_with_reference(new, "tree", &size, 0);
 	if (!tree)
 		die("unable to read root tree (%s)", sha1_to_hex(new));
 	retval = diff_tree("", 0, tree, size, base);
 	free(tree);
-	if (generate_patch)
-		diff_flush();
+	diff_flush();
 	return retval;
 }
 
@@ -485,8 +468,9 @@ int main(int argc, char **argv)
 			recursive = generate_patch = 1;
 			continue;
 		}
-		if (!strcmp(arg, "-M")) {
+		if (!strncmp(arg, "-M", 2)) {
 			detect_rename = recursive = generate_patch = 1;
+			diff_score_opt = diff_scoreopt_parse(arg);
 			continue;
 		}
 		if (!strcmp(arg, "-z")) {

diff.c

@@ -11,6 +11,8 @@
 
 static const char *diff_opts = "-pu";
 static unsigned char null_sha1[20] = { 0, };
+#define MAX_SCORE 10000
+#define DEFAULT_MINIMUM_SCORE 5000
 
 static const char *external_diff(void)
 {
@@ -55,7 +57,7 @@ static char *sq_expand(const char *src)
 	const char *cp;
 	char *bp;
 
-	/* count bytes needed to store the quoted string. */ 
+	/* count bytes needed to store the quoted string. */
 	for (cnt = 1, cp = src; *cp; cnt++, cp++)
 		if (*cp == '\'')
 			cnt += 3;
@@ -93,7 +95,8 @@ struct diff_spec {
 
 static void builtin_diff(const char *name_a,
 			 const char *name_b,
-			 struct diff_tempfile *temp)
+			 struct diff_tempfile *temp,
+			 int rename_score)
 {
 	int i, next_at, cmd_size;
 	const char *diff_cmd = "diff -L'%s%s' -L'%s%s'";
@@ -149,6 +152,10 @@ static void builtin_diff(const char *name_a,
 			printf("new mode %s\n", temp[1].mode);
 		}
 		if (strcmp(name_a, name_b)) {
+			if (0 < rename_score)
+				printf("rename similarity index %d%%\n",
+				       (int)(0.5+
+					     rename_score*100.0/MAX_SCORE));
 			printf("rename old %s\n", name_a);
 			printf("rename new %s\n", name_b);
 		}
@@ -184,7 +191,7 @@ static int work_tree_matches(const char *name, const unsigned char *sha1)
 	 * file.  Practically, this code only helps when we are used
 	 * by diff-cache --cached, which does read the cache before
 	 * calling us.
-	 */ 
+	 */
 	if (!active_cache)
 		return 0;
 
@@ -302,9 +309,10 @@ static void remove_tempfile_on_signal(int signo)
 
 static int detect_rename;
 static int reverse_diff;
+static int diff_raw_output = -1;
 static const char **pathspec;
 static int speccnt;
-static int diff_rename_minimum_score;
+static int minimum_score;
 
 static int matches_pathspec(const char *name)
 {
@@ -334,7 +342,8 @@ static int matches_pathspec(const char *name)
 static void run_external_diff(const char *name,
 			      const char *other,
 			      struct diff_spec *one,
-			      struct diff_spec *two)
+			      struct diff_spec *two,
+			      int rename_score)
 {
 	struct diff_tempfile *temp = diff_temp;
 	pid_t pid;
@@ -395,7 +404,7 @@ static void run_external_diff(const char *name,
 		 * otherwise we use the built-in one.
 		 */
 		if (one && two)
-			builtin_diff(name, other ? : name, temp);
+			builtin_diff(name, other ? : name, temp, rename_score);
 		else
 			printf("* Unmerged path %s\n", name);
 		exit(0);
@@ -446,7 +455,7 @@ static void hold_diff(const char *name,
 		die("internal error");
 
 	if (!detect_rename) {
-		run_external_diff(name, NULL, one, two);
+		run_external_diff(name, NULL, one, two, -1);
 		return;
 	}
 	elem = xmalloc(sizeof(*elem) + strlen(name));
@@ -519,10 +528,10 @@ static void flush_remaining_diff(struct diff_spec_hold *elem,
 			continue;
 		if (on_created_list)
 			run_external_diff(elem->path, NULL,
-					  &null_file_spec, &elem->it);
+					  &null_file_spec, &elem->it, -1);
 		else
 			run_external_diff(elem->path, NULL,
-					  &elem->it, &null_file_spec);
+					  &elem->it, &null_file_spec, -1);
 	}
 }
 
@@ -541,7 +550,6 @@ static int is_exact_match(struct diff_spec_hold *src,
 	return 0;
 }
 
-#define MINIMUM_SCORE 5000
 int estimate_similarity(struct diff_spec_hold *src, struct diff_spec_hold *dst)
 {
 	/* src points at a deleted file and dst points at a created
@@ -549,20 +557,24 @@ int estimate_similarity(struct diff_spec_hold *src, struct diff_spec_hold *dst)
 	 * say src is renamed to dst.
 	 *
 	 * Compare them and return how similar they are, representing
-	 * the score as an integer between 0 and 10000.  10000 is
-	 * reserved for the case where they match exactly.
+	 * the score as an integer between 0 and 10000, except
+	 * where they match exactly it is considered better than anything
+	 * else.
 	 */
 	void *delta;
 	unsigned long delta_size;
+	int score;
 
 	delta_size = ((src->size < dst->size) ?
 		      (dst->size - src->size) : (src->size - dst->size));
 
 	/* We would not consider rename followed by more than
-	 * 20% edits; that is, delta_size must be smaller than
-	 * (src->size + dst->size)/2 * 0.2, which means...
+	 * minimum_score/MAX_SCORE edits; that is, delta_size must be smaller
+	 * than (src->size + dst->size)/2 * minimum_score/MAX_SCORE,
+	 * which means...
 	 */
-	if ((src->size + dst->size) < delta_size * 10)
+
+	if ((src->size+dst->size)*minimum_score < delta_size*MAX_SCORE*2)
 		return 0;
 
 	delta = diff_delta(src->data, src->size,
@@ -573,14 +585,17 @@ int estimate_similarity(struct diff_spec_hold *src, struct diff_spec_hold *dst)
 	/* This "delta" is really xdiff with adler32 and all the
 	 * overheads but it is a quick and dirty approximation.
 	 *
-	 * Now we will give some score to it.  Let's say 20% edit gets
-	 * 5000 points and 0% edit gets 9000 points.  That is, every
-	 * 1/20000 edit gets 1 point penalty.  The amount of penalty is:
+	 * Now we will give some score to it.  100% edit gets
+	 * 0 points and 0% edit gets MAX_SCORE points.  That is, every
+	 * 1/MAX_SCORE edit gets 1 point penalty.  The amount of penalty is:
 	 *
-	 * (delta_size * 2 / (src->size + dst->size)) * 20000
+	 * (delta_size * 2 / (src->size + dst->size)) * MAX_SCORE
 	 *
 	 */
-	return 9000 - (40000 * delta_size / (src->size+dst->size));
+	score = MAX_SCORE-(MAX_SCORE*2*delta_size/(src->size+dst->size));
+	if (score < 0) return 0;
+	if (MAX_SCORE < score) return MAX_SCORE;
+	return score;
 }
 
 struct diff_score {
@@ -596,14 +611,15 @@ static int score_compare(const void *a_, const void *b_)
 }
 
 static void flush_rename_pair(struct diff_spec_hold *src,
-			      struct diff_spec_hold *dst)
+			      struct diff_spec_hold *dst,
+			      int rename_score)
 {
 	src->flags |= MATCHED;
 	dst->flags |= MATCHED;
 	free_data(src);
 	free_data(dst);
 	run_external_diff(src->path, dst->path,
-			  &src->it, &dst->it);
+			  &src->it, &dst->it, rename_score);
 }
 
 static void free_held_diff(struct diff_spec_hold *list)
@@ -637,7 +653,7 @@ void diff_flush(void)
 				continue;
 			if (! is_exact_match(src, dst))
 				continue;
-			flush_rename_pair(src, dst);
+			flush_rename_pair(src, dst, MAX_SCORE);
 			break;
 		}
 	}
@@ -670,7 +686,7 @@ void diff_flush(void)
 		}
 		c++;
 	}
-	qsort(mx, num_create*num_delete, sizeof(*mx), score_compare); 
+	qsort(mx, num_create*num_delete, sizeof(*mx), score_compare);
 
 #if 0
  	for (c = 0; c < num_create * num_delete; c++) {
@@ -689,9 +705,9 @@ void diff_flush(void)
 		dst = mx[c].dst;
 		if ((src->flags & MATCHED) || (dst->flags & MATCHED))
 			continue;
-		if (mx[c].score < diff_rename_minimum_score)
+		if (mx[c].score < minimum_score)
 			break;
-		flush_rename_pair(src, dst);
+		flush_rename_pair(src, dst, mx[c].score);
 	}
 	free(mx);
 
@@ -703,7 +719,26 @@ void diff_flush(void)
 	createdfile = deletedfile = NULL;
 }
 
+int diff_scoreopt_parse(const char *opt)
+{
+	int diglen, num, scale, i;
+	if (opt[0] != '-' || opt[1] != 'M')
+		return -1; /* that is not -M option */
+	diglen = strspn(opt+2, "0123456789");
+	if (diglen == 0 || strlen(opt+2) != diglen)
+		return 0; /* use default */
+	sscanf(opt+2, "%d", &num);
+	for (i = 0, scale = 1; i < diglen; i++)
+		scale *= 10;
+
+	/* user says num divided by scale and we say internally that
+	 * is MAX_SCORE * num / scale.
+	 */
+	return MAX_SCORE * num / scale;
+}
+
 void diff_setup(int detect_rename_, int minimum_score_, int reverse_diff_,
+		int diff_raw_output_,
 		const char **pathspec_, int speccnt_)
 {
 	free_held_diff(createdfile);
@@ -713,8 +748,14 @@ void diff_setup(int detect_rename_, int minimum_score_, int reverse_diff_,
 	detect_rename = detect_rename_;
 	reverse_diff = reverse_diff_;
 	pathspec = pathspec_;
+	diff_raw_output = diff_raw_output_;
 	speccnt = speccnt_;
-	diff_rename_minimum_score = minimum_score_ ? : MINIMUM_SCORE;
+	minimum_score = minimum_score_ ? : DEFAULT_MINIMUM_SCORE;
+}
+
+static const char *git_object_type(unsigned mode)
+{
+	return S_ISDIR(mode) ? "tree" : "blob";
 }
 
 void diff_addremove(int addremove, unsigned mode,
@@ -724,6 +765,21 @@ void diff_addremove(int addremove, unsigned mode,
 	char concatpath[PATH_MAX];
 	struct diff_spec spec[2], *one, *two;
 
+	if (0 <= diff_raw_output) {
+		if (!path)
+			path = "";
+		if (reverse_diff)
+			addremove = (addremove == '+' ? '-' : '+');
+		printf("%c%06o %s %s %s%s%c",
+		       addremove,
+		       mode,
+		       git_object_type(mode), sha1_to_hex(sha1),
+		       base, path, diff_raw_output);
+		return;
+	}
+	if (S_ISDIR(mode))
+		return;
+
 	memcpy(spec[0].blob_sha1, sha1, 20);
 	spec[0].mode = mode;
 	spec[0].sha1_valid = !!memcmp(sha1, null_sha1, 20);
@@ -750,6 +806,29 @@ void diff_change(unsigned old_mode, unsigned new_mode,
 	char concatpath[PATH_MAX];
 	struct diff_spec spec[2];
 
+	if (0 <= diff_raw_output) {
+		char old_hex[41];
+		strcpy(old_hex, sha1_to_hex(old_sha1));
+
+		if (!path)
+			path = "";
+		if (reverse_diff)
+			printf("*%06o->%06o %s %s->%s %s%s%c",
+			       new_mode, old_mode,
+			       git_object_type(new_mode),
+			       sha1_to_hex(new_sha1), old_hex,
+			       base, path, diff_raw_output);
+		else
+			printf("*%06o->%06o %s %s->%s %s%s%c",
+			       old_mode, new_mode,
+			       git_object_type(new_mode),
+			       old_hex, sha1_to_hex(new_sha1),
+			       base, path, diff_raw_output);
+		return;
+	}
+	if (S_ISDIR(new_mode))
+		return;
+
 	if (path) {
 		strcpy(concatpath, base);
 		strcat(concatpath, path);
@@ -766,10 +845,15 @@ void diff_change(unsigned old_mode, unsigned new_mode,
 	/* We do not look at changed files as candidate for
 	 * rename detection ever.
 	 */
-	run_external_diff(path ? concatpath : base, NULL, &spec[0], &spec[1]);
+	run_external_diff(path ? concatpath : base, NULL,
+			  &spec[0], &spec[1], -1);
 }
 
 void diff_unmerge(const char *path)
 {
-	run_external_diff(path, NULL, NULL, NULL);
+	if (0 <= diff_raw_output) {
+		printf("U %s%c", path, diff_raw_output);
+		return;
+	}
+	run_external_diff(path, NULL, NULL, NULL, -1);
 }

diff.h

@@ -17,8 +17,10 @@ extern void diff_change(unsigned mode1, unsigned mode2,
 
 extern void diff_unmerge(const char *path);
 
+extern int diff_scoreopt_parse(const char *opt);
+
 extern void diff_setup(int detect_rename, int minimum_score,
-		       int reverse,
+		       int reverse, int raw_output,
 		       const char **spec, int cnt);
 
 extern void diff_flush(void);

t/t0000-basic.sh

@@ -166,7 +166,7 @@ cat >expected <<\EOF
 EOF
 test_expect_success \
     'validate git-diff-files output for a know cache/work tree state.' \
-    'git-diff-files >current && cmp -s current expected'
+    'git-diff-files >current && diff >/dev/null -b current expected'
 
 test_expect_success \
     'git-update-cache --refresh should succeed.' \

t/t2002-checkout-cache-u.sh

@@ -29,3 +29,5 @@ rm -f path0 &&
 git-read-tree $t &&
 git-checkout-cache -u -f -a &&
 git-diff-files | diff - /dev/null'
+
+test_done

t/t4001-diff-rename.sh

@@ -58,3 +58,9 @@ rename new path1
  Line 13
  Line 14
 EOF
+
+test_expect_success \
+    'validate the output.' \
+    'diff -I "rename similarity.*" >/dev/null current expected'
+
+test_done