read_sha1_file(): report correct name of packfile with a corrupt object

Clarify the error reporting logic by moving the normal codepath (i.e. we
read the object we wanted to read correctly) up and return early.

The logic to report the name of the packfile with a corrupt object,
introduced by e8b15e6 (sha1_file: Show the the type and path to corrupt
objects, 2010-06-10), was totally bogus.  The function that knows which
bad object came from what packfile is has_packed_and_bad(); make it report
which packfile the problem was found.

"Corrupt" is already an adjective, e.g. an object is "corrupt"; we do not
have to say "corrupted object".

Signed-off-by: Junio C Hamano <gitster@pobox.com>

sha1_file.c

@@ -1003,16 +1003,16 @@ static void mark_bad_packed_object(struct packed_git *p,
 	p->num_bad_objects++;
 }
 
-static int has_packed_and_bad(const unsigned char *sha1)
+static const struct packed_git *has_packed_and_bad(const unsigned char *sha1)
 {
 	struct packed_git *p;
 	unsigned i;
 
 	for (p = packed_git; p; p = p->next)
 		for (i = 0; i < p->num_bad_objects; i++)
 			if (!hashcmp(sha1, p->bad_object_sha1 + 20 * i))
-				return 1;
-	return 0;
+				return p;
+	return NULL;
 }
 
 int check_sha1_signature(const unsigned char *sha1, void *map, unsigned long size, const char *type)
@@ -2079,6 +2079,11 @@ static void *read_object(const unsigned char *sha1, enum object_type *type,
 	return read_packed_sha1(sha1, type, size);
 }
 
+/*
+ * This function dies on corrupt objects; the callers who want to
+ * deal with them should arrange to call read_object() and give error
+ * messages themselves.
+ */
 void *read_sha1_file_repl(const unsigned char *sha1,
 			  enum object_type *type,
 			  unsigned long *size,
@@ -2087,28 +2092,30 @@ void *read_sha1_file_repl(const unsigned char *sha1,
 	const unsigned char *repl = lookup_replace_object(sha1);
 	void *data = read_object(repl, type, size);
 	char *path;
+	const struct packed_git *p;
+
+	if (data) {
+		if (replacement)
+			*replacement = repl;
+		return data;
+	}
 
 	/* die if we replaced an object with one that does not exist */
-	if (!data && repl != sha1)
+	if (repl != sha1)
 		die("replacement %s not found for %s",
 		    sha1_to_hex(repl), sha1_to_hex(sha1));
 
-	/* legacy behavior is to die on corrupted objects */
-	if (!data) {
-		if (has_loose_object(repl)) {
-			path = sha1_file_name(sha1);
-			die("loose object %s (stored in %s) is corrupted", sha1_to_hex(repl), path);
-		}
-		if (has_packed_and_bad(repl)) {
-			path = sha1_pack_name(sha1);
-			die("packed object %s (stored in %s) is corrupted", sha1_to_hex(repl), path);
-		}
+	if (has_loose_object(repl)) {
+		path = sha1_file_name(sha1);
+		die("loose object %s (stored in %s) is corrupt",
+		    sha1_to_hex(repl), path);
 	}
 
-	if (replacement)
-		*replacement = repl;
+	if ((p = has_packed_and_bad(repl)) != NULL)
+		die("packed object %s (stored in %s) is corrupt",
+		    sha1_to_hex(repl), p->pack_name);
 
-	return data;
+	return NULL;
 }
 
 void *read_object_with_reference(const unsigned char *sha1,