[PATCH] Redo rename/copy detection logic.

Earlier implementation had a major screw-up in the memory
management area.  Rename/copy logic sometimes borrowed a pointer
to a structure without any provision for downstream to determine
which pointer is shared and which is not.  This resulted in the
later clean-up code to sometimes double free such structure,
resulting in a segfault.  This made -M and -C useless.

Another problem the earlier implementation had was that it
reordered the patches, and forced the logic to differentiate
renames and copies to depend on that particular order.  This
problem was fixed by teaching rename/copy detection logic not to
do any reordering, and rename-copy differentiator not to depend
on the order of the patches.  The diffs will leave rename/copy
detector in the same destination path order as the patch that
was fed into it.  Some test vectors have been reordered to
accommodate this change.

It also adds a sanity check logic to the human-readable diff-raw
output to detect paths with embedded TAB and LF characters,
which cannot be expressed with that format.  This idea came up
during a discussion with Chris Wedgwood.

Signed-off-by: Junio C Hamano <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

diff.c

@@ -493,8 +493,6 @@ struct diff_filepair *diff_queue(struct diff_queue_struct *queue,
 	dp->one = one;
 	dp->two = two;
 	dp->score = 0;
-	dp->orig_order = queue->nr;
-	dp->rename_rank = 0;
 	diff_q(queue, dp);
 	return dp;
 }
@@ -505,6 +503,17 @@ static void diff_flush_raw(struct diff_filepair *p,
 {
 	int two_paths;
 	char status[10];
+
+	if (line_termination) {
+		const char *err = "path %s cannot be expressed without -z";
+		if (strchr(p->one->path, line_termination) ||
+		    strchr(p->one->path, inter_name_termination))
+			die(err, p->one->path);
+		if (strchr(p->two->path, line_termination) ||
+		    strchr(p->two->path, inter_name_termination))
+			die(err, p->two->path);
+	}
+
 	switch (p->status) {
 	case 'C': case 'R':
 		two_paths = 1;
@@ -628,41 +637,110 @@ int diff_needs_to_stay(struct diff_queue_struct *q, int i,
 int diff_queue_is_empty(void)
 {
 	struct diff_queue_struct *q = &diff_queued_diff;
-	return q->nr == 0;
+	int i;
+	for (i = 0; i < q->nr; i++)
+		if (!diff_unmodified_pair(q->queue[i]))
+			return 0;
+	return 1;
 }
 
-static void diff_resolve_rename_copy(void)
+#if DIFF_DEBUG
+void diff_debug_filespec(struct diff_filespec *s, int x, const char *one)
+{
+	fprintf(stderr, "queue[%d] %s (%s) %s %06o %s\n",
+		x, one ? : "",
+		s->path,
+		DIFF_FILE_VALID(s) ? "valid" : "invalid",
+		s->mode,
+		s->sha1_valid ? sha1_to_hex(s->sha1) : "");
+	fprintf(stderr, "queue[%d] %s size %lu flags %d\n",
+		x, one ? : "",
+		s->size, s->xfrm_flags);
+}
+
+void diff_debug_filepair(const struct diff_filepair *p, int i)
+{
+	diff_debug_filespec(p->one, i, "one");
+	diff_debug_filespec(p->two, i, "two");
+	fprintf(stderr, "score %d, status %c\n",
+		p->score, p->status ? : '?');
+}
+
+void diff_debug_queue(const char *msg, struct diff_queue_struct *q)
 {
 	int i;
-	struct diff_queue_struct *q = &diff_queued_diff;
+	if (msg)
+		fprintf(stderr, "%s\n", msg);
+	fprintf(stderr, "q->nr = %d\n", q->nr);
 	for (i = 0; i < q->nr; i++) {
 		struct diff_filepair *p = q->queue[i];
+		diff_debug_filepair(p, i);
+	}
+}
+#endif
+
+static void diff_resolve_rename_copy(void)
+{
+	int i, j;
+	struct diff_filepair *p, *pp;
+	struct diff_queue_struct *q = &diff_queued_diff;
+
+	/* This should not depend on the ordering of things. */
+
+	diff_debug_queue("resolve-rename-copy", q);
+
+	for (i = 0; i < q->nr; i++) {
+		p = q->queue[i];
 		p->status = 0;
 		if (DIFF_PAIR_UNMERGED(p))
 			p->status = 'U';
 		else if (!DIFF_FILE_VALID((p)->one))
 			p->status = 'N';
 		else if (!DIFF_FILE_VALID((p)->two)) {
-			/* maybe earlier one said 'R', meaning
-			 * it will take it, in which case we do
-			 * not need to keep 'D'.
+			/* Deletion record should be omitted if there
+			 * is another entry that is a rename or a copy
+			 * and it uses this one as the source.  Then we
+			 * can say the other one is a rename.
 			 */
-			int j;
-			for (j = 0; j < i; j++) {
-				struct diff_filepair *pp = q->queue[j];
-				if (pp->status == 'R' &&
-				    !strcmp(pp->one->path, p->one->path))
+			for (j = 0; j < q->nr; j++) {
+				pp = q->queue[j];
+				if (!strcmp(pp->one->path, p->one->path) &&
+				    strcmp(pp->one->path, pp->two->path))
 					break;
 			}
-			if (j < i)
-				continue;
+			if (j < q->nr)
+				continue; /* has rename/copy */
 			p->status = 'D';
 		}
 		else if (strcmp(p->one->path, p->two->path)) {
-			/* This is rename or copy.  Which one is it? */
-			if (diff_needs_to_stay(q, i+1, p->one))
-				p->status = 'C';
-			else
+			/* See if there is somebody else anywhere that
+			 * will keep the path (either modified or
+			 * unmodified).  If so, we have to be a copy,
+			 * not a rename.  In addition, if there is
+			 * some other rename or copy that comes later
+			 * than us that uses the same source, we
+			 * cannot be a rename either.
+			 */
+			for (j = 0; j < q->nr; j++) {
+				pp = q->queue[j];
+				if (strcmp(pp->one->path, p->one->path))
+					continue;
+				if (!strcmp(pp->one->path, pp->two->path)) {
+					if (DIFF_FILE_VALID(pp->two)) {
+						/* non-delete */
+						p->status = 'C';
+						break;
+					}
+					continue;
+				}
+				/* pp is a rename/copy ... */
+				if (i < j) {
+					/* ... and comes later than us */
+					p->status = 'C';
+					break;
+				}
+			}
+			if (!p->status)
 				p->status = 'R';
 		}
 		else if (memcmp(p->one->sha1, p->two->sha1, 20))
@@ -672,6 +750,7 @@ static void diff_resolve_rename_copy(void)
 			p->status = 0;
 		}
 	}
+	diff_debug_queue("resolve-rename-copy done", q);
 }
 
 void diff_flush(int diff_output_style, int resolve_rename_copy)