diff --git a/Makefile b/Makefile
index 6910448ef2..2aa2385b6b 100644
--- a/Makefile
+++ b/Makefile
@@ -182,7 +182,7 @@ LIB_H = \
 
 DIFF_OBJS = \
 	diff.o diffcore-break.o diffcore-order.o diffcore-pathspec.o \
-	diffcore-pickaxe.o diffcore-rename.o tree-diff.o
+	diffcore-pickaxe.o diffcore-rename.o tree-diff.o combine-diff.o
 
 LIB_OBJS = \
 	blob.o commit.o connect.o count-delta.o csum-file.o \
diff --git a/combine-diff.c b/combine-diff.c
new file mode 100644
index 0000000000..669002349a
--- /dev/null
+++ b/combine-diff.c
@@ -0,0 +1,469 @@
+#include "cache.h"
+#include "commit.h"
+#include "diff.h"
+#include "diffcore.h"
+#include "quote.h"
+
+struct path_list {
+	struct path_list *next;
+	int len;
+	char *path;
+	unsigned char sha1[20];
+	unsigned char parent_sha1[FLEX_ARRAY][20];
+};
+
+static int uninteresting(struct diff_filepair *p)
+{
+	if (diff_unmodified_pair(p))
+		return 1;
+	if (!S_ISREG(p->one->mode) || !S_ISREG(p->two->mode))
+		return 1;
+	return 0;
+}
+
+static struct path_list *intersect_paths(struct path_list *curr,
+					 int n, int num_parent)
+{
+	struct diff_queue_struct *q = &diff_queued_diff;
+	struct path_list *p;
+	int i;
+
+	if (!n) {
+		struct path_list *list = NULL, *tail = NULL;
+		for (i = 0; i < q->nr; i++) {
+			int len;
+			const char *path;
+			if (uninteresting(q->queue[i]))
+				continue;
+			path = q->queue[i]->two->path;
+			len = strlen(path);
+
+			p = xmalloc(sizeof(*p) + len + 1 + num_parent * 20);
+			p->path = (char*) &(p->parent_sha1[num_parent][0]);
+			memcpy(p->path, path, len);
+			p->path[len] = 0;
+			p->len = len;
+			p->next = NULL;
+			memcpy(p->sha1, q->queue[i]->two->sha1, 20);
+			memcpy(p->parent_sha1[n], q->queue[i]->one->sha1, 20);
+			if (!tail)
+				list = tail = p;
+			else {
+				tail->next = p;
+				p = tail;
+			}
+		}
+		return list;
+	}
+
+	for (p = curr; p; p = p->next) {
+		int found = 0;
+		if (!p->len)
+			continue;
+		for (i = 0; i < q->nr; i++) {
+			const char *path;
+			int len;
+
+			if (uninteresting(q->queue[i]))
+				continue;
+			path = q->queue[i]->two->path;
+			len = strlen(path);
+			if (len == p->len && !memcmp(path, p->path, len)) {
+				found = 1;
+				memcpy(p->parent_sha1[n],
+				       q->queue[i]->one->sha1, 20);
+				break;
+			}
+		}
+		if (!found)
+			p->len = 0;
+	}
+	return curr;
+}
+
+struct lline {
+	struct lline *next;
+	int len;
+	unsigned long parent_map;
+	char line[FLEX_ARRAY];
+};
+
+struct sline {
+	struct lline *lost_head, **lost_tail;
+	char *bol;
+	int len;
+	unsigned long flag;
+};
+
+static char *grab_blob(const unsigned char *sha1, unsigned long *size)
+{
+	char *blob;
+	char type[20];
+	if (!memcmp(sha1, null_sha1, 20)) {
+		/* deleted blob */
+		*size = 0;
+		return xcalloc(1, 1);
+	}
+	blob = read_sha1_file(sha1, type, size);
+	if (strcmp(type, "blob"))
+		die("object '%s' is not a blob!", sha1_to_hex(sha1));
+	return blob;
+}
+
+#define TMPPATHLEN 50
+#define MAXLINELEN 10240
+
+static void write_to_temp_file(char *tmpfile, void *blob, unsigned long size)
+{
+	int fd = git_mkstemp(tmpfile, TMPPATHLEN, ".diff_XXXXXX");
+	if (fd < 0)
+		die("unable to create temp-file");
+	if (write(fd, blob, size) != size)
+		die("unable to write temp-file");
+	close(fd);
+}
+
+static void write_temp_blob(char *tmpfile, const unsigned char *sha1)
+{
+	unsigned long size;
+	void *blob;
+	blob = grab_blob(sha1, &size);
+	write_to_temp_file(tmpfile, blob, size);
+	free(blob);
+}
+
+static int parse_num(char **cp_p, unsigned int *num_p)
+{
+	char *cp = *cp_p;
+	unsigned int num = 0;
+	int read_some;
+
+	while ('0' <= *cp && *cp <= '9')
+		num = num * 10 + *cp++ - '0';
+	if (!(read_some = cp - *cp_p))
+		return -1;
+	*cp_p = cp;
+	*num_p = num;
+	return 0;
+}
+
+static int parse_hunk_header(char *line, int len,
+			     unsigned int *ob, unsigned int *on,
+			     unsigned int *nb, unsigned int *nn)
+{
+	char *cp;
+	cp = line + 4;
+	if (parse_num(&cp, ob)) {
+	bad_line:
+		return error("malformed diff output: %s", line);
+	}
+	if (*cp == ',') {
+		cp++;
+		if (parse_num(&cp, on))
+			goto bad_line;
+	}
+	else
+		*on = 1;
+	if (*cp++ != ' ' || *cp++ != '+')
+		goto bad_line;
+	if (parse_num(&cp, nb))
+		goto bad_line;
+	if (*cp == ',') {
+		cp++;
+		if (parse_num(&cp, nn))
+			goto bad_line;
+	}
+	else
+		*nn = 1;
+	return -!!memcmp(cp, " @@", 3);
+}
+
+static void append_lost(struct sline *sline, int n, const char *line)
+{
+	struct lline *lline;
+	int len = strlen(line);
+	unsigned long this_mask = (1UL<<n);
+	if (line[len-1] == '\n')
+		len--;
+
+	/* Check to see if we can squash things */
+	if (sline->lost_head) {
+		struct lline *last_one = NULL;
+		/* We cannot squash it with earlier one */
+		for (lline = sline->lost_head;
+		     lline;
+		     lline = lline->next)
+			if (lline->parent_map & this_mask)
+				last_one = lline;
+		lline = last_one ? last_one->next : sline->lost_head;
+		while (lline) {
+			if (lline->len == len &&
+			    !memcmp(lline->line, line, len)) {
+				lline->parent_map |= this_mask;
+				return;
+			}
+			lline = lline->next;
+		}
+	}
+
+	lline = xmalloc(sizeof(*lline) + len + 1);
+	lline->len = len;
+	lline->next = NULL;
+	lline->parent_map = this_mask;
+	memcpy(lline->line, line, len);
+	lline->line[len] = 0;
+	if (sline->lost_head)
+		*(sline->lost_tail) = lline;
+	else
+		sline->lost_head = lline;
+	sline->lost_tail = &lline->next;
+}
+
+static void combine_diff(const unsigned char *parent, const char *ourtmp,
+			 struct sline *sline, int cnt, int n)
+{
+	FILE *in;
+	char parent_tmp[TMPPATHLEN];
+	char cmd[TMPPATHLEN * 2 + 1024];
+	char line[MAXLINELEN];
+	unsigned int lno, ob, on, nb, nn;
+	unsigned long pmask = ~(1UL << n);
+	struct sline *lost_bucket = NULL;
+
+	write_temp_blob(parent_tmp, parent);
+	sprintf(cmd, "diff --unified=0 -La/x -Lb/x '%s' '%s'",
+		parent_tmp, ourtmp);
+	in = popen(cmd, "r");
+	if (!in)
+		return;
+
+	lno = 1;
+	while (fgets(line, sizeof(line), in) != NULL) {
+		int len = strlen(line);
+		if (5 < len && !memcmp("@@ -", line, 4)) {
+			if (parse_hunk_header(line, len,
+					      &ob, &on, &nb, &nn))
+				break;
+			lno = nb;
+			if (!nb) {
+				/* @@ -1,2 +0,0 @@ to remove the
+				 * first two lines...
+				 */
+				nb = 1;
+			}
+			lost_bucket = &sline[nb-1]; /* sline is 0 based */
+			continue;
+		}
+		if (!lost_bucket)
+			continue;
+		switch (line[0]) {
+		case '-':
+			append_lost(lost_bucket, n, line+1);
+			break;
+		case '+':
+			sline[lno-1].flag &= pmask;
+			lno++;
+			break;
+		}
+	}
+	fclose(in);
+	unlink(parent_tmp);
+}
+
+static unsigned long context = 3;
+static char combine_marker = '@';
+
+static int interesting(struct sline *sline, unsigned long all_mask)
+{
+	return ((sline->flag & all_mask) != all_mask || sline->lost_head);
+}
+
+static void make_hunks(struct sline *sline, unsigned long cnt, int num_parent)
+{
+	unsigned long all_mask = (1UL<<num_parent) - 1;
+	unsigned long mark = (1UL<<num_parent);
+	unsigned long i;
+
+	i = 0;
+	while (i < cnt) {
+		if (interesting(&sline[i], all_mask)) {
+			unsigned long j = (context < i) ? i - context : 0;
+			while (j <= i)
+				sline[j++].flag |= mark;
+			while (++i < cnt) {
+				if (!interesting(&sline[i], all_mask))
+					break;
+				sline[i].flag |= mark;
+			}
+			j = (i + context < cnt) ? i + context : cnt;
+			while (i < j)
+				sline[i++].flag |= mark;
+			continue;
+		}
+		i++;
+	}
+}
+
+static void dump_sline(struct sline *sline, int cnt, int num_parent)
+{
+	unsigned long mark = (1UL<<num_parent);
+	int i;
+	int lno = 0;
+
+	while (1) {
+		struct sline *sl = &sline[lno];
+		int hunk_end;
+		while (lno < cnt && !(sline[lno].flag & mark))
+			lno++;
+		if (cnt <= lno)
+			break;
+		for (hunk_end = lno + 1; hunk_end < cnt; hunk_end++)
+			if (!(sline[hunk_end].flag & mark))
+				break;
+		for (i = 0; i <= num_parent; i++) putchar(combine_marker);
+		printf(" +%d,%d ", lno+1, hunk_end-lno);
+		for (i = 0; i <= num_parent; i++) putchar(combine_marker);
+		putchar('\n');
+		while (lno < hunk_end) {
+			struct lline *ll;
+			int j;
+			sl = &sline[lno++];
+			ll = sl->lost_head;
+			while (ll) {
+				for (j = 0; j < num_parent; j++) {
+					if (ll->parent_map & (1UL<<j))
+						putchar('-');
+					else
+						putchar(' ');
+				}
+				putchar(' ');
+				puts(ll->line);
+				ll = ll->next;
+			}
+			for (j = 0; j < num_parent; j++) {
+				if ((1UL<<j) & sl->flag)
+					putchar(' ');
+				else
+					putchar('+');
+			}
+			printf(" %.*s\n", sl->len, sl->bol);
+		}
+	}
+}
+
+static void show_combined_diff(struct path_list *elem, int num_parent)
+{
+	unsigned long size, cnt, lno;
+	char *result, *cp, *ep;
+	struct sline *sline; /* survived lines */
+	int i;
+	char ourtmp[TMPPATHLEN];
+
+	/* Read the result of merge first */
+	result = grab_blob(elem->sha1, &size);
+	write_to_temp_file(ourtmp, result, size);
+
+	for (cnt = 0, cp = result; cp - result < size; cp++) {
+		if (*cp == '\n')
+			cnt++;
+	}
+	if (result[size-1] != '\n')
+		cnt++; /* incomplete line */
+
+	sline = xcalloc(cnt, sizeof(*sline));
+	ep = result;
+	sline[0].bol = result;
+	for (lno = 0, cp = result; cp - result < size; cp++) {
+		if (*cp == '\n') {
+			sline[lno].len = cp - sline[lno].bol;
+			sline[lno].flag = (1UL<<num_parent) - 1;
+			lno++;
+			if (lno < cnt)
+				sline[lno].bol = cp + 1;
+		}
+	}
+	if (result[size-1] != '\n') {
+		sline[cnt-1].len = size - (sline[cnt-1].bol - result);
+		sline[cnt-1].flag = (1UL<<num_parent) - 1;
+	}
+
+	for (i = 0; i < num_parent; i++)
+		combine_diff(elem->parent_sha1[i], ourtmp, sline, cnt, i);
+
+	make_hunks(sline, cnt, num_parent);
+
+	dump_sline(sline, cnt, num_parent);
+	unlink(ourtmp);
+	free(result);
+
+	for (i = 0; i < cnt; i++) {
+		if (sline[i].lost_head) {
+			struct lline *ll = sline[i].lost_head;
+			while (ll) {
+				struct lline *tmp = ll;
+				ll = ll->next;
+				free(tmp);
+			}
+		}
+	}
+	free(sline);
+}
+
+int diff_tree_combined_merge(const unsigned char *sha1,
+			     const char *header, int show_empty_merge)
+{
+	struct commit *commit = lookup_commit(sha1);
+	struct diff_options diffopts;
+	struct commit_list *parents;
+	struct path_list *p, *paths = NULL;
+	int num_parent, i, num_paths;
+
+	diff_setup(&diffopts);
+	diffopts.output_format = DIFF_FORMAT_NO_OUTPUT;
+	diffopts.recursive = 1;
+
+	/* count parents */
+	for (parents = commit->parents, num_parent = 0;
+	     parents;
+	     parents = parents->next, num_parent++)
+		; /* nothing */
+
+	/* find set of paths that everybody touches */
+	for (parents = commit->parents, i = 0;
+	     parents;
+	     parents = parents->next, i++) {
+		struct commit *parent = parents->item;
+		diff_tree_sha1(parent->object.sha1, commit->object.sha1, "",
+			       &diffopts);
+		paths = intersect_paths(paths, i, num_parent);
+		diff_flush(&diffopts);
+	}
+
+	/* find out surviving paths */
+	for (num_paths = 0, p = paths; p; p = p->next) {
+		if (p->len)
+			num_paths++;
+	}
+	if (num_paths || show_empty_merge) {
+		puts(header);
+		for (p = paths; p; p = p->next) {
+			if (!p->len)
+				continue;
+			printf("diff --combined ");
+			if (quote_c_style(p->path, NULL, NULL, 0))
+				quote_c_style(p->path, NULL, stdout, 0);
+			else
+				printf("%s", p->path);
+			putchar('\n');
+			show_combined_diff(p, num_parent);
+		}
+	}
+
+	/* Clean things up */
+	while (paths) {
+		struct path_list *tmp = paths;
+		paths = paths->next;
+		free(tmp);
+	}
+	return 0;
+}
diff --git a/diff-tree.c b/diff-tree.c
index efa2b9476e..0c689360ee 100644
--- a/diff-tree.c
+++ b/diff-tree.c
@@ -6,6 +6,8 @@ static int show_root_diff = 0;
 static int no_commit_id = 0;
 static int verbose_header = 0;
 static int ignore_merges = 1;
+static int show_empty_combined = 0;
+static int combine_merges = 0;
 static int read_stdin = 0;
 
 static const char *header = NULL;
@@ -79,9 +81,13 @@ static const char *generate_header(const unsigned char *commit_sha1,
 	offset = sprintf(this_header, "%s%s ",
 			 header_prefix,
 			 diff_unique_abbrev(commit_sha1, abbrev));
-	offset += sprintf(this_header + offset, "(from %s)\n",
-			 parent_sha1 ?
-			 diff_unique_abbrev(parent_sha1, abbrev) : "root");
+	if (commit_sha1 != parent_sha1)
+		offset += sprintf(this_header + offset, "(from %s)\n",
+				  parent_sha1
+				  ? diff_unique_abbrev(parent_sha1, abbrev)
+				  : "root");
+	else
+		offset += sprintf(this_header + offset, "(from parents)\n");
 	offset += pretty_print_commit(commit_format, msg, len,
 				      this_header + offset,
 				      sizeof(this_header) - offset);
@@ -108,8 +114,16 @@ static int diff_tree_commit(const unsigned char *commit_sha1)
 	}
 
 	/* More than one parent? */
-	if (ignore_merges && commit->parents && commit->parents->next)
-		return 0;
+	if (commit->parents && commit->parents->next) {
+		if (ignore_merges)
+			return 0;
+		else if (combine_merges) {
+			header = generate_header(sha1, sha1,
+						 commit->buffer);
+			return diff_tree_combined_merge(sha1, header,
+							show_empty_combined);
+		}
+	}
 
 	for (parents = commit->parents; parents; parents = parents->next) {
 		struct commit *parent = parents->item;
@@ -154,7 +168,7 @@ static int diff_tree_stdin(char *line)
 }
 
 static const char diff_tree_usage[] =
-"git-diff-tree [--stdin] [-m] [-s] [-v] [--pretty] [-t] [-r] [--root] "
+"git-diff-tree [--stdin] [-m] [-c] [-s] [-v] [--pretty] [-t] [-r] [--root] "
 "[<common diff options>] <tree-ish> [<tree-ish>] [<path>...]\n"
 "  -r            diff recursively\n"
 "  --root        include the initial commit as diff against /dev/null\n"
@@ -217,6 +231,10 @@ int main(int argc, const char **argv)
 			ignore_merges = 0;
 			continue;
 		}
+		if (!strcmp(arg, "-c")) {
+			combine_merges = 1;
+			continue;
+		}
 		if (!strcmp(arg, "-v")) {
 			verbose_header = 1;
 			header_prefix = "diff-tree ";
@@ -245,6 +263,12 @@ int main(int argc, const char **argv)
 	if (diff_options.output_format == DIFF_FORMAT_PATCH)
 		diff_options.recursive = 1;
 
+	if (combine_merges) {
+		diff_options.output_format = DIFF_FORMAT_PATCH;
+		show_empty_combined = !ignore_merges;
+		ignore_merges = 0;
+	}
+
 	diff_tree_setup_paths(get_pathspec(prefix, argv));
 	diff_setup_done(&diff_options);
 
diff --git a/diff.h b/diff.h
index 5696f2aff0..081234cb97 100644
--- a/diff.h
+++ b/diff.h
@@ -56,6 +56,8 @@ extern int diff_tree(struct tree_desc *t1, struct tree_desc *t2,
 extern int diff_tree_sha1(const unsigned char *old, const unsigned char *new,
 			  const char *base, struct diff_options *opt);
 
+extern int diff_tree_combined_merge(const unsigned char *sha1, const char *, int);
+
 extern void diff_addremove(struct diff_options *,
 			   int addremove,
 			   unsigned mode,