diff --git a/show-diff.c b/show-diff.c
index 4557bd82f3..993668e014 100644
--- a/show-diff.c
+++ b/show-diff.c
@@ -4,10 +4,11 @@
  * Copyright (C) Linus Torvalds, 2005
  */
 #include "cache.h"
+#include "diff.h"
 
-static const char *show_diff_usage = "show-diff [-q] [-s] [-z] [paths...]";
+static const char *show_diff_usage = "show-diff [-q] [-s] [-z] [-p] [paths...]";
 
-static int recursive = 0;
+static int generate_patch = 0;
 static int line_termination = '\n';
 static int silent = 0;
 static int silent_on_nonexisting_files = 0;
@@ -27,27 +28,57 @@ static int matches_pathspec(struct cache_entry *ce, char **spec, int cnt)
 	return 0;
 }
 
-static void show_file(const char *prefix, struct cache_entry *ce)
+static void show_unmerge(const char *path)
 {
-	printf("%s%o\t%s\t%s\t%s%c", prefix, ntohl(ce->ce_mode), "blob",
-		sha1_to_hex(ce->sha1), ce->name, line_termination);
+	if (generate_patch)
+		diff_unmerge(path);
+	else
+		printf("U %s%c", path, line_termination);
+}
+
+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);
+}
+
+static void show_modified(int oldmode, int mode,
+			  const char *old_sha1, const 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);
 }
 
 int main(int argc, char **argv)
 {
-	static const char null_sha1_hex[] = "0000000000000000000000000000000000000000";
+	static const char null_sha1[20] = { 0, };
 	int entries = read_cache();
 	int i;
 
 	while (1 < argc && argv[1][0] == '-') {
 		if (!strcmp(argv[1], "-s"))
 			silent_on_nonexisting_files = silent = 1;
+		else if (!strcmp(argv[1], "-p"))
+			generate_patch = 1;
 		else if (!strcmp(argv[1], "-q"))
 			silent_on_nonexisting_files = 1;
 		else if (!strcmp(argv[1], "-z"))
 			line_termination = 0;
 		else if (!strcmp(argv[1], "-r"))
-			recursive = 1;		/* No-op */
+			; /* no-op */
 		else
 			usage(show_diff_usage);
 		argv++; argc--;
@@ -72,8 +103,7 @@ int main(int argc, char **argv)
 			continue;
 
 		if (ce_stage(ce)) {
-			printf("U %s%c", ce->name, line_termination);
-
+			show_unmerge(ce->name);
 			while (i < entries &&
 			       !strcmp(ce->name, active_cache[i]->name))
 				i++;
@@ -88,7 +118,7 @@ int main(int argc, char **argv)
 			}	
 			if (silent_on_nonexisting_files)
 				continue;
-			show_file("-", ce);
+			show_file('-', ce);
 			continue;
 		}
 		changed = cache_match_stat(ce, &st);
@@ -98,10 +128,8 @@ int main(int argc, char **argv)
 		oldmode = ntohl(ce->ce_mode);
 		mode = S_IFREG | ce_permissions(st.st_mode);
 
-		printf("*%o->%o\t%s\t%s->%s\t%s%c",
-			oldmode, mode, "blob",
-			sha1_to_hex(ce->sha1), null_sha1_hex,
-			ce->name, line_termination);
+		show_modified(oldmode, mode, ce->sha1, null_sha1,
+			      ce->name);
 	}
 	return 0;
 }